Cardiovascular drugs: Practice MCQs

Answer: B. Conversion of angiotensin I to angiotensin II by angiotensin-converting enzyme

ACE inhibitors are competitive inhibitors of angiotensin-converting enzyme and prevent the conversion of angiotensin I to angiotensin II. Renin cleaves angiotensinogen upstream of that step, and the mineralocorticoid receptor and neprilysin are the targets of entirely different classes.

Answer: C. The same enzyme also degrades bradykinin, so inhibiting it raises kinin concentrations in the lung

Angiotensin-converting enzyme metabolises bradykinin and other local molecules as well as angiotensin I. Inhibiting the enzyme in the lung increases kinin concentrations and causes bronchial irritation, which is why the cough is a mechanism effect rather than an allergy, and why it is reported in roughly 10% to 20% of patients.

Answer: B. Lisinopril and captopril

Lisinopril and captopril are not prodrugs. Enalapril, fosinopril, benazepril, quinapril and moexipril all require hepatic conversion to their active forms, which is why a non-prodrug is preferred in a patient with underlying liver disease.

Answer: B. Reduced angiotensin II means reduced aldosterone, and without aldosterone less potassium is secreted into the urine

Blocking angiotensin II removes the downstream stimulus to aldosterone secretion. Aldosterone normally drives sodium reabsorption with secretion of potassium and protons into the urine, so its loss allows potassium to accumulate. Reduced kidney function or a potassium-retaining co-prescription increases the risk.

Answer: C. Enalapril, given intravenously as enalaprilat

All ACE inhibitors are prescribed orally except enalapril, which can also be given intravenously. Enalaprilat is the only intravenous member of the class and has a rapid onset of action, which is what makes it useful in a hypertensive emergency.

Answer: A. They are contraindicated in the second and third trimesters because of a documented fetopathy

ACE inhibitors are contraindicated during the second and third trimesters because of a well-documented fetopathy. Reported effects include oligohydramnios, decreased fetal renal function, anuria, renal failure, skull hypoplasia and death, and a strong association with major cardiovascular and neurological malformations has also been described after first-trimester exposure.

Answer: B. The drug lowers ACE concentrations in peripheral blood, so the result cannot be interpreted accurately

ACE inhibitors potentially lead to low ACE concentrations in peripheral blood samples, so the clinical interpretation of that measurement in a patient with sarcoidosis receiving one of these drugs is not accurate.

Answer: B. It covalently acetylates a serine residue in the cyclooxygenase-1 active site, abolishing enzyme activity irreversibly

Aspirin transfers its acetyl group to a serine residue in the cyclooxygenase-1 active site. Because the modification is covalent and the anucleate platelet cannot make new enzyme, thromboxane A2 production stays suppressed for the lifespan of that platelet.

Answer: C. Clopidogrel

Clopidogrel is a prodrug whose two-step bioactivation depends on CYP2C19. A loss-of-function allele leaves the patient unable to generate sufficient active metabolite, producing high on-treatment platelet reactivity.

Answer: C. Ticagrelor

Ticagrelor and its metabolite interact reversibly with the platelet P2Y12 receptor, while clopidogrel and prasugrel are prodrugs whose active metabolites block the receptor irreversibly.

Answer: B. Cangrelor occupies the P2Y12 receptor so densely that thienopyridine active metabolites cannot bind

High receptor occupancy by cangrelor prevents the active metabolites of clopidogrel and prasugrel from reaching the receptor, so those agents are started once the infusion has been discontinued. Ticagrelor is the stated exception.

Answer: C. Prasugrel

Prasugrel is contraindicated after a prior stroke or transient ischaemic attack because of the heightened risk of haemorrhage in that group, and it separately carries a boxed warning for potentially fatal bleeding.

Answer: B. Phosphodiesterase inhibitors demonstrated decreased survival compared with placebo in class III to IV heart failure

The restriction is a mortality signal rather than a bleeding one: phosphodiesterase inhibitors showed decreased survival compared with placebo in advanced heart failure, so cilostazol is avoided across grades of heart failure.

Answer: A. A recognised and common effect of ticagrelor itself

Dyspnoea occurred in about a fifth of patients in the THEMIS population, was usually mild to moderate in intensity, and often resolved during continued treatment. It still warrants clinical assessment, but it is a known drug effect rather than an unexplained finding.

Answer: C. There is no specific antidote for any antiplatelet drug, so care is supportive and may include blood products

No specific antidote exists for any antiplatelet medication. Management centres on supportive care, and resuscitation with blood products including packed red blood cells and platelets may be necessary for severe haemorrhage.

Answer: A. Propranolol, carvedilol, sotalol and labetalol are non-selective; atenolol, bisoprolol, metoprolol and esmolol are beta-1 selective

Non-selective agents bind both beta-1 and beta-2 receptors and include propranolol, carvedilol, sotalol and labetalol. Beta-1 selective, or cardioselective, agents include atenolol, bisoprolol, metoprolol and esmolol.

Answer: B. Acebutolol

Acebutolol is described as a cardioselective beta-adrenoceptor blocking agent possessing mild intrinsic sympathomimetic activity in its therapeutically effective dose range. Metoprolol, by contrast, has neither membrane stabilising nor intrinsic sympathomimetic activity.

Answer: B. It produces rebound sympathetic activation with a rise in heart rate and blood pressure and a heightened risk of adverse cardiovascular events

Sudden withdrawal of beta blockade leads to rebound sympathetic activation, raising heart rate and blood pressure and increasing cardiovascular risk, particularly where there is coronary artery disease or heart failure. That is the reasoning behind a structured, gradual taper rather than an immediate stop.

Answer: C. Carvedilol and labetalol vasodilate through alpha-adrenergic blockade, while nebivolol does so through nitric oxide

Carvedilol and labetalol carry additional alpha-1 receptor blocking activity alongside non-selective beta blockade. Nebivolol achieves vasodilation differently, by stimulating endothelial nitric oxide synthase through beta-3 agonism and so reducing systemic vascular resistance.

Answer: C. Sotalol

Sotalol blocks cardiac potassium channels in addition to beta receptors and is classified as a class III antiarrhythmic. That potassium channel blockade prolongs the QT interval and increases the risk of torsades de pointes, so the QTc interval requires monitoring.

Answer: B. Glucagon

Glucagon is the antidote for beta-blocker overdose and is particularly useful in beta-blocker-induced cardiotoxicity. Cardiac pacing, whether transcutaneous or transvenous, is the second-line option when glucagon fails.

Answer: C. Both depress atrioventricular nodal conduction and myocardial contractility, so the combination increases the likelihood of bradycardia, heart block or acute decompensated heart failure

Beta blockers and verapamil act on the same two properties — atrioventricular nodal conduction and myocardial contractility — so their effects add. The combination should follow a clear indication and close monitoring, especially where conduction disease or left ventricular dysfunction is present, and even systemically absorbed ophthalmic timolol can contribute.

Answer: A. Esmolol

Esmolol is typically used in intensive care or cardiac inpatient settings for refractory tachycardia such as atrial fibrillation, because its short onset of action and short half-life make it titratable.

Answer: B. Class Ia prolongs the QTc, class Ib shortens it, class Ic does not affect it

Class Ia prolongs action potential duration and therefore increases the QTc interval. Class Ib decreases action potential duration and shortens the QTc. Class Ic does not affect action potential duration, so it leaves the QTc interval unchanged.

Answer: C. They increased mortality in patients with a previous myocardial infarction compared with placebo

The Cardiac Arrhythmia Suppression Trials showed increased mortality in patients who had a previous myocardial infarction and were treated with class Ic agents rather than placebo. That result is the reason class Ic agents are contraindicated in structural heart disease and are avoided where left ventricular dysfunction is present.

Answer: B. Because flecainide can convert atrial fibrillation to atrial flutter with one-to-one conduction

Flecainide can convert atrial fibrillation into atrial flutter that conducts one-to-one through the atrioventricular node, producing a dangerously fast ventricular response. A beta blocker or a calcium channel blocker is therefore used concurrently to slow nodal conduction.

Answer: C. Lidocaine and mexiletine, used for ventricular arrhythmias especially after myocardial infarction

Class Ib comprises lidocaine and mexiletine. These agents cause mild sodium channel blockade with rapid kinetics, shorten the QTc interval and are directed at ventricular arrhythmias, particularly in the post-infarct setting. They are not helpful for atrial arrhythmias.

Answer: B. Quinidine causing cinchonism

Cinchonism is the recognised quinidine adverse effect and presents with tinnitus, hearing loss, vision disturbance and confusion. Drug-induced lupus points to procainamide, anticholinergic features such as dry skin and urinary retention point to disopyramide, and the class Ib toxicity picture is different again.

Answer: A. Bone marrow toxicity, including agranulocytosis and pancytopenia

Procainamide is known to cause bone marrow toxicity, with agranulocytosis and pancytopenia described. It is separately associated with a lupus-like reaction featuring positive antinuclear antibody titres, arthritis, arthralgias and pleuritis on chronic use.

Answer: B. Sodium bicarbonate

Sodium bicarbonate is the cornerstone of treatment for sodium channel blocker toxicity. It raises serum pH and increases extracellular sodium, which widens the electrochemical gradient across the cell membrane and helps to offload the blocked sodium channels.

Answer: C. Disopyramide

Disopyramide is the class Ia agent described for hypertrophic obstructive cardiomyopathy, used together with a beta blocker or with verapamil. Quinidine's distinctive indications are Brugada syndrome and short QT syndrome, while procainamide features in Wolff-Parkinson-White syndrome with atrial fibrillation and in terminating ventricular tachycardia.

Answer: B. They exert minimal direct effects on the myocardium and act primarily as peripheral vasodilators at therapeutic doses

Both groups bind L-type voltage-gated calcium channels, but the dihydropyridines have minimal direct myocardial effect and behave as peripheral vasodilators at therapeutic doses, whereas the non-dihydropyridines inhibit the sinoatrial and atrioventricular nodes and slow conduction and contractility.

Answer: C. Selective arteriolar dilation raises intracapillary pressure and drives fluid into the interstitial space

These agents selectively dilate arterioles, which increases intracapillary pressure and causes extravasation of fluid into the interstitium. Because the mechanism is redistribution rather than salt and water retention, the oedema does not respond to the reflex of adding a diuretic.

Answer: B. A prescribing cascade, in which a drug adverse effect is mistaken for a new medical condition

A prescribing cascade occurs when the drug-induced oedema is mistaken for a new condition and a diuretic is added to treat it. Evaluating whether the oedema is attributable to an underlying condition or to the drug is the risk mitigation step; an ACE inhibitor or angiotensin receptor blocker can also prevent the oedema.

Answer: C. Nimodipine

Nimodipine was originally developed to manage systemic hypertension, but its current use is restricted primarily to the prevention and treatment of cerebral vasospasm following subarachnoid haemorrhage, where it reduces the incidence and severity of ischaemic deficits.

Answer: B. Because immediate-release preparations caused rapid vasodilation followed by reflex sympathetic activation with headaches, palpitations and flushing

The original short-acting immediate-release formulations required multiple daily doses and produced rapid vasodilation with reflex sympathetic activation, causing headaches, palpitations and flushing. Extended-release preparations were introduced because they give a sustained antihypertensive effect with fewer adverse effects.

Answer: B. CYP3A4

Calcium channel blockers are extensively hepatically metabolised, primarily by CYP3A4, and many have low bioavailability because of that first-pass metabolism. Inhibitors such as azole antifungals, macrolides, protease inhibitors and grapefruit juice raise exposure, while inducers such as carbamazepine, phenytoin and rifampicin lower it.

Answer: B. Beta-islet cells depend on calcium influx through L-type channels to release insulin, so blockade reduces insulin release

Pancreatic beta-islet cells depend on calcium influx through L-type calcium channels for insulin release, so blockade reduces insulin secretion and hyperglycaemia follows. It has been considered a prognostic indicator of the severity of toxicity, and the same insulin blockade impairs myocardial glucose uptake.

Answer: B. Reflex tachycardia may occur in mild-to-moderate overdose, but selectivity can be lost in severe poisoning, producing bradycardia

Dihydropyridines in mild-to-moderate overdose may cause reflex tachycardia. In severe poisoning, receptor selectivity may be lost, leading to bradycardia, so the pulse alone does not identify which subclass has been taken.

Answer: B. Cyclic GMP, via guanylyl cyclase

Nitrates release nitric oxide, which activates guanylyl cyclase. That enzyme converts guanosine triphosphate into cyclic GMP, and the rise in cyclic GMP activates protein kinases that lower calcium availability and inactivate myosin light chain kinase, relaxing the muscle.

Answer: A. Venous capacitance vessels

Nitrates dilate venous capacitance vessels, arterioles and coronary arteries, but the maximal effect is seen in the venous capacitance vessels. Pooling blood there reduces preload and therefore myocardial oxygen demand.

Answer: C. It does not undergo the hepatic first-pass effect

Isosorbide dinitrate undergoes an extensive first-pass effect in the liver, which cuts oral bioavailability to around 20% and leaves an elimination half-life of about one hour. Isosorbide mononitrate does not undergo that first-pass step, so bioavailability after oral administration is 100% and the half-life is five to six hours.

Answer: B. Within 12 to 24 hours; prevented by a daily nitrate-free interval

Tolerance may develop within as little as 12 to 24 hours, with a subsequent loss of clinical effect. A drug-free interval of at least 10 to 12 hours a day is what maintains responsiveness, and continuous intravenous infusion is a recognised route to tolerance.

Answer: B. Because both drugs raise cyclic GMP, and the combination can cause life-threatening hypotension

Phosphodiesterase-5 inhibitors such as sildenafil, vardenafil and tadalafil accentuate the hypotensive effect of nitrates and can precipitate syncope. The combined rise in cyclic GMP produces hypotension described as life-threatening, which is why the combination is listed as absolutely contraindicated.

Answer: C. Right ventricular infarction

In right ventricular infarction, the reduction in preload produced by a nitrate can cause profound hypotension leading to cardiogenic shock. It is listed among the contraindications for that reason.

Answer: B. Tachycardia, dizziness and headache on re-exposure to nitrate after a drug-free interval

Monday disease arises from the tolerance that develops during continuous nitrate exposure. After a drug-free interval, re-exposure produces tachycardia, dizziness and headache as the vasodilator response returns.

Answer: A. Methaemoglobinaemia

Nitrate ions released during metabolism can oxidise haemoglobin into methaemoglobin, which cannot carry oxygen in the normal way. Blood gas analysis with co-oximetry is what confirms it, and methylene blue is the described antidote.

Answer: A. Competitive inhibition of HMG-CoA reductase, which converts HMG-CoA to mevalonate

Statins are selective, competitive inhibitors of HMG-CoA reductase, the rate-limiting enzyme of the cholesterol synthesis pathway. The other three options describe ezetimibe, the fibrates and the bile acid sequestrants respectively.

Answer: B. Because lower hepatocyte cholesterol upregulates LDL receptors, increasing hepatic uptake of LDL

The fall in intracellular cholesterol triggers upregulation of LDL receptors on the hepatocyte surface, and it is the increased receptor-mediated uptake that clears LDL from the circulation.

Answer: B. Clarithromycin inhibits CYP3A4, and simvastatin is a CYP3A4 substrate, so exposure and myopathy risk rise

Simvastatin, together with atorvastatin and lovastatin, is metabolised by CYP3A4. Inhibitors of that enzyme — including macrolides, azole antifungals, protease inhibitors, amiodarone, diltiazem and verapamil — increase statin exposure and therefore myopathy risk.

Answer: C. Gemfibrozil

Gemfibrozil reduces the metabolism of simvastatin, raising its concentration and the risk of myopathy, and the pairing is described as a combination to avoid. Gemfibrozil with pravastatin carries a similar myopathy risk.

Answer: C. Liver tests are checked before starting, with retesting only if symptoms arise, because serious injury is rare

Multiple academic societies and the regulator recommend baseline testing with retesting only if symptoms appear. Serious hepatotoxicity is rare and unpredictable, and statins are considered usable in non-alcoholic fatty liver disease.

Answer: B. Rosuvastatin and pravastatin

Rosuvastatin and pravastatin are the hydrophilic members; atorvastatin, simvastatin, fluvastatin, pitavastatin and lovastatin are lipophilic. Lipophilic agents penetrate tissues by passive diffusion, whereas hydrophilic ones depend on transporter proteins.

Answer: A. Active hepatic disease or unexplained persistent aminotransferase elevation

Active hepatic disease and unexplained persistent aminotransferase elevations are contraindications, alongside breastfeeding and pregnancy, the latter with an exception recognised in 2021 regulatory guidance for patients at high cardiovascular risk. Familial hypercholesterolaemia is an indication, not a contraindication.

Answer: B. The proximal segment of the distal convoluted tubule, blocking the Na+/Cl- channel

The defining action is blockade of the sodium-chloride channel in the proximal segment of the distal convoluted tubule. The Na-K-2Cl cotransporter of the thick ascending limb belongs to loop diuretics, and the epithelial sodium channel of the collecting duct belongs to the potassium-sparing agents.

Answer: B. Increased sodium delivery to the distal nephron activates aldosterone-mediated pumps that excrete potassium and hydrogen ions

The potassium loss is a downstream consequence. Sodium that escapes reabsorption in the distal convoluted tubule reaches the aldosterone-sensitive segment, where sodium uptake is coupled to potassium and hydrogen ion secretion, which also explains the accompanying metabolic alkalosis.

Answer: C. Hypercalcaemia

Thiazide blockade of the Na+/Cl- channel increases flow through the Na+/Ca2+ exchanger and therefore calcium reabsorption, so calcium rises. Loop diuretics do the opposite and cause loss of calcium and magnesium. Hypokalaemia, alkalosis and hyperuricaemia occur with both.

Answer: A. Thiazides directly increase urate reabsorption in the proximal tubule

Hyperuricaemia is a recognised thiazide adverse effect, and the recorded mechanism is a direct increase in urate reabsorption in the proximal tubule. Uric acid is therefore one of the values monitored during therapy.

Answer: B. The class loses effectiveness as filtration rate falls, but chlorthalidone, metolazone and indapamide maintain efficacy at low filtration rates

Diuretic and antihypertensive effect declines across the class as glomerular filtration rate falls, but chlorthalidone, metolazone and indapamide are documented exceptions that keep working below 30 mL/min/1.73 m2. Anuria is a contraindication, not an indication.

Answer: B. Anuria and sulfonamide allergy

Anuria and sulfonamide allergy are the contraindications recorded for the class. Because the parent structure is a sulfonamide, an allergy history redirects the choice of diuretic rather than simply intensifying monitoring.

Answer: B. To achieve sequential nephron blockade, one of the documented responses to chronic tolerance to loop diuretics

Chronic tolerance to loop diuretics reflects distal tubular structural adaptation, and co-administering a thiazide-like diuretic blocks that adapted segment as well — a deliberate sequential blockade. It intensifies rather than corrects the shared electrolyte risks, so monitoring becomes more, not less, important.

Answer: B. They block alpha-2 autoreceptors, increasing norepinephrine release, which then stimulates beta receptors

Alpha-2 receptors on peripheral nerve endings normally inhibit norepinephrine release. Blocking them removes that feedback, and the resulting norepinephrine spillover stimulates beta receptors, producing tremulousness and tachycardia.

Answer: C. Alfuzosin, tamsulosin and silodosin

Alfuzosin, tamsulosin and silodosin have relatively minimal orthostatic adverse effects and are considered first-line for this condition. Doxazosin, prazosin and terazosin are effective but are not preferred because of their adverse effect profile.

Answer: A. First-dose hypotension with syncope and dizziness

Selective alpha-1 blockers cause first-dose hypotension, syncope, dizziness and headache through vasodilation and vascular smooth muscle relaxation. These effects are commoner in older patients and increase the risk of falls, which is why night-time administration is recommended.

Answer: B. Intraoperative floppy iris syndrome

Intraoperative floppy iris syndrome can occur during cataract surgery and, while associated with any selective alpha blocker, is most commonly linked to tamsulosin. Features include iris billowing, prolapse through surgical incisions and progressive pupillary constriction despite mydriatic therapy.

Answer: B. Phenoxybenzamine is irreversible and phentolamine is reversible

Both are non-selective agents approved for managing phaeochromocytoma, but phenoxybenzamine is an irreversible alpha blocker while phentolamine is reversible. Phentolamine is also used for cocaine-induced cardiovascular complications, where beta blockade risks unopposed alpha-mediated vasoconstriction.

Answer: B. Because alpha-1 blockade relaxes vascular smooth muscle and also relaxes smooth muscle in the prostate and bladder neck

Selective alpha-1 antagonists lower blood pressure by preventing norepinephrine from activating alpha-1 receptors on vascular smooth muscle, and they relieve obstructive urinary symptoms by relaxing smooth muscle in the prostate and bladder neck to facilitate urine flow.

Answer: C. Supportive care: supine positioning, fluid resuscitation if hypotension persists, and vasopressors as a last resort

No specific antidote is available. The hypotensive patient is positioned supine until blood pressure and heart rate stabilise, fluid resuscitation follows if hypotension persists, and vasopressors are reserved as a last resort.

Answer: C. They selectively block angiotensin II at the type 1 receptor

ARBs selectively inhibit the binding of angiotensin II to the angiotensin type 1 receptor. Direct renin inhibitors act on renin production, ACE inhibitors prevent the conversion of angiotensin I to angiotensin II, and aldosterone antagonists work at the mineralocorticoid receptor — four different points on the same pathway.

Answer: B. ARBs do not elevate bradykinin, which is the mediator responsible for the cough

The incidence of cough and angio-oedema with ARBs is lower than with ACE inhibitors because ARBs do not elevate bradykinin levels. The cough on an ACE inhibitor is caused by kinin accumulation in the lung, so a drug that leaves bradykinin metabolism alone removes the cause.

Answer: B. Losartan

Among ARBs, losartan functions as a uricosuric agent by inhibiting urate transporter 1 in the renal proximal tubules, thereby lowering uric acid levels. This is specific to losartan and is not shared by the rest of the class.

Answer: C. Olmesartan

Olmesartan has been associated with sprue-like enteropathy. Other rare adverse effects reported across the class include urticaria, anaphylaxis, vasculitis, neutropenia, leukopenia and liver function test abnormalities.

Answer: B. It is strongly advised against, because of increased adverse events

KDIGO strongly advises against combining ACE inhibitors, ARBs and direct renin inhibitors in individuals with chronic kidney disease, regardless of diabetes status, because of the increased risk of adverse events. The combination raises the risk of hypotension, acute renal failure and hyperkalaemia.

Answer: C. Telmisartan — not metabolised by CYP enzymes, half-life of about 24 hours, predominantly hepatic clearance

Telmisartan is not metabolised by CYP enzymes and instead undergoes conjugation, primarily glucuronidation. Its terminal half-life is approximately 24 hours and hepatic clearance accounts for the majority of its elimination. Irbesartan's bioavailability is 60% to 80%, and losartan is not a prodrug — candesartan, olmesartan and azilsartan are.

Answer: B. Pregnancy

ARBs, like ACE inhibitors, are contraindicated during pregnancy because of the risk of reduced fetal kidney perfusion, which may lead to renal dysgenesis, oliguric or anuric renal failure, oligohydramnios, skeletal or skull deformities, pulmonary hypoplasia and fetal death. Therapy should be discontinued immediately if pregnancy is detected.

Answer: B. By reversibly inhibiting the sodium-potassium ATPase pump, which raises intracellular calcium

Digoxin reversibly inhibits the myocardial sodium-potassium ATPase pump. Intracellular sodium rises, which drives an influx of calcium into the heart muscle cell through sodium-calcium exchange, and the extra calcium enhances contractility.

Answer: C. By a vagomimetic effect that slows conduction through the atrioventricular node

Digoxin exerts vagomimetic effects on the atrioventricular node by stimulating the parasympathetic nervous system. This prolongs the node's refractory period, slows electrical conduction through it and therefore reduces the ventricular rate.

Answer: A. Hypokalaemia, hypomagnesaemia and hypercalcaemia

Low potassium, low magnesium and high calcium all increase susceptibility to digoxin's effects. Loop diuretics frequently contribute to the hypokalaemia, which is why electrolyte monitoring is part of using the drug safely.

Answer: B. Bidirectional ventricular tachycardia

Bidirectional ventricular tachycardia, in which the QRS complexes alternate from beat to beat, is described as pathognomonic for toxicity. Premature ventricular complexes are the most common rhythm disturbance, and digoxin can produce almost every type of arrhythmia.

Answer: B. It rises, because inhibition of the sodium-potassium ATPase blocks potassium re-entry into cells

Acute toxicity causes hyperkalaemia through inhibition of the sodium-potassium ATPase. Chronic toxicity is different: it commonly develops in a patient who is already hypokalaemic from diuretic use and reduced clearance.

Answer: B. Yellow or green tinted vision, known as xanthopsia

Colour vision change with a yellow or green tint, called xanthopsia, is typically associated with digoxin toxicity. Photophobia, photopsia and reduced visual acuity are also described, alongside gastrointestinal upset and confusion.

Answer: B. Because laboratory assays cannot distinguish free digoxin from digoxin bound to the antibody fragment

Assays cannot tell free digoxin from digoxin bound to the Fab fragment, so results read falsely high even though most of the measured drug is bound and cannot reach the cardiac sodium-potassium ATPase. Accurate levels require waiting about three weeks after administration.

Answer: A. Intravenous calcium

Intravenous administration of calcium is contraindicated in people taking digoxin, with rapid intravenous calcium capable of inducing severe arrhythmias. Activated charcoal, glucose with insulin for life-threatening hyperkalaemia, and atropine for bradycardia are all described within the management of toxicity.

Answer: B. Niemann-Pick C1-Like 1 at the brush border of the small intestine

Ezetimibe is a selective cholesterol-absorption inhibitor acting on the NPC1L1 sterol transporter at the intestinal brush border, which is what makes its mechanism distinct from every other lipid-lowering class.

Answer: B. By reducing cholesterol delivery to the liver, lowering hepatic cholesterol stores and increasing clearance from the blood

Less cholesterol arriving from the gut means lower hepatic stores, and the liver compensates by clearing more cholesterol from the circulation. Total cholesterol, LDL and triglycerides fall while HDL rises modestly.

Answer: B. Around 13% to 20%

Monotherapy reduces LDL cholesterol by roughly 13% to 20%, which is why the drug is usually positioned as an addition to statin therapy rather than a replacement for it.

Answer: A. Ciclosporin

Ciclosporin increases ezetimibe exposure by a factor reported between about 2.3 and 12, and ciclosporin concentrations themselves require monitoring when the two are combined.

Answer: C. Ezetimibe and a bile acid sequestrant

Ezetimibe must be given at an interval either before or after a bile acid sequestrant, because the resin binds it. Statins and fibrates may be co-administered without a time separation, though the myopathy risk of those combinations still applies.

Answer: B. Ezetimibe alone has not been associated with a higher rate of ALT elevation than placebo, while adding it to a statin slightly increases that likelihood

Monotherapy does not raise the ALT elevation rate above placebo, and combination with a statin produces only a slight increase. Clinically apparent acute liver injury has been reported but is rare.

Answer: A. Because bile acid sequestrants can cause a significant further increase in triglycerides

A significant increase in triglycerides is a recognised effect of colesevelam, so both markedly raised triglycerides and a history of hypertriglyceridaemia-induced pancreatitis are listed as contraindications, alongside a history of bowel obstruction.

Answer: B. Blockade of potassium channels, prolonging recovery and the refractory period

Class III agents block potassium channels. That prolongs action potential recovery in atrial, Purkinje and ventricular muscle cells, increases the effective refractory period, reduces repolarisation reserve and lengthens the QT interval on the electrocardiogram.

Answer: C. It also blocks beta-adrenergic receptors, calcium channels and sodium channels

Amiodarone inhibits the potassium rectifier currents that repolarise the heart during phase 3, which is the class III action, but it additionally blocks beta-adrenergic receptors, calcium channels and sodium channels. That combined profile also reduces sinoatrial node automaticity and slows atrioventricular node conduction.

Answer: A. Corneal microdeposits

Corneal microdeposits are reported in at least 90% of patients on amiodarone. Photophobia, optic neuropathy and visual halos are described in far fewer, and the skin and lung effects are separate parts of the toxicity profile.

Answer: B. Because it shows reverse use-dependence, with maximum potassium blockade at slower rates

Sotalol exhibits reverse use-dependent effects: the maximum potassium channel blockade occurs at slower heart rates. That increases QT prolongation and arrhythmia risk during bradycardia rather than during fast rhythms.

Answer: B. Primarily in bile, with less than 1% excreted unchanged in urine

Amiodarone is metabolised in the liver by cytochrome P450 enzymes and eliminated primarily by the biliary route, with less than 1% excreted unchanged in the urine. Its half-life is several weeks and its absorption is variable, ranging from 22% to 86%.

Answer: C. Permanent atrial fibrillation

Dronedarone is contraindicated in permanent atrial fibrillation, and also in pregnancy. Its licensed role is oral treatment of paroxysmal or persistent atrial fibrillation or flutter. The PALLAS trial, conducted specifically in patients with permanent atrial fibrillation, was stopped early because of an increased rate of primary outcome events including death — which is exactly why the contraindication is worded around permanent atrial fibrillation.

Answer: A. Intravenous magnesium

Intravenous magnesium is described as the first-line pharmacological therapy for torsades de pointes. Correction of electrolyte abnormalities, synchronised cardioversion and overdrive pacing for refractory cases are the other elements of management.

Answer: A. Warfarin, whose clearance is reduced, and digoxin, whose concentration can double

Amiodarone reduces warfarin clearance, so close monitoring of the international normalised ratio is advised. It can also produce a notable increase in digoxin concentrations, potentially doubling them, and it interferes with the metabolism of lovastatin and atorvastatin.

Answer: B. The Na-K-2Cl (NKCC2) cotransporter at the apical membrane of the thick ascending limb

Loop diuretics compete with chloride to bind the Na-K-2Cl cotransporter on the apical membrane of the thick ascending limb, inhibiting sodium and chloride reabsorption at the segment that handles a large fraction of the filtered load.

Answer: C. Blocking the cotransporter prevents the potassium recycling that sustains the gradient driving calcium and magnesium reabsorption

Blockade of the Na-K-2Cl cotransporter leaves potassium unable to return to the lumen, and the resulting loss of the electrical driving force means calcium and magnesium ions are lost with the urine.

Answer: B. After large bolus doses given in an acute setting, producing high serum concentrations

Deafness and tinnitus most frequently follow large bolus doses in acute settings, and the toxicity is attributed to the higher serum concentrations reached. Renal impairment and concurrent aminoglycosides or platinum agents raise the risk further.

Answer: D. Ethacrynic acid

Ethacrynic acid stands apart chemically from the other members and is therefore the safer option where a sulfonamide allergy is a concern. It is, however, the most ototoxic agent in the group and has been linked to permanent sensorineural hearing loss.

Answer: B. Rebound sodium retention from increased distal tubular reabsorption after a dose, representing acute tolerance

Acute tolerance develops some time after a dose and causes rebound retention of sodium through increased reabsorption in the distal tubules. Correct dose selection, dosing frequency, timing of diet and dietary salt restriction are the described countermeasures.

Answer: B. Furosemide oral bioavailability averages about 50%, lower and more variable than bumetanide or torsemide at around 80%

Average oral bioavailability of furosemide is around 50%, whereas bumetanide and torsemide reach approximately 80%. That difference is one reason a change of agent or of route can restore a response without any change in the underlying disease.

Answer: A. Anuria

Anuria is listed alongside hypersensitivity to the drug or to sulfonamides, hepatic coma and severe electrolyte depletion. Hypercalcaemia is not a contraindication, since the class increases rather than reduces calcium excretion.

Answer: B. They exert inhibitory effects on the sinoatrial and atrioventricular nodes, slowing cardiac conduction and contractility

Both groups bind L-type voltage-gated calcium channels, but the non-dihydropyridines inhibit the sinoatrial and atrioventricular nodes, slowing conduction and contractility. That property allows them to treat hypertension, reduce oxygen demand and control the rate of tachydysrhythmias.

Answer: B. Both depress atrioventricular nodal conduction and myocardial contractility, so bradycardia, heart block or acute decompensated heart failure become more likely

Their effects add on the same two properties. The combination should be prescribed only with a clear indication and close monitoring, particularly where conduction disease or left ventricular dysfunction is present, and even systemically absorbed ophthalmic timolol can contribute.

Answer: A. Atrial fibrillation or flutter associated with an accessory bypass tract

Atrial fibrillation or flutter associated with an accessory bypass tract, as in Wolff-Parkinson-White syndrome, is a contraindication for both drugs. The other three options are approved indications rather than contraindications.

Answer: B. Verapamil, a phenylalkylamine, and diltiazem, a benzothiazepine

The non-dihydropyridines are verapamil, classified as a phenylalkylamine, and diltiazem, classified as a benzothiazepine. The dihydropyridines are the separate group whose members mostly end in -pine.

Answer: B. They inhibit CYP3A and P-glycoprotein as well as being metabolised by CYP3A4

Verapamil and diltiazem inhibit the CYP3A isoenzyme, raising concentrations of ciclosporin, statins, benzodiazepines, buspirone and sildenafil, and they inhibit P-glycoprotein, which raises digoxin, dabigatran and colchicine levels among others.

Answer: B. Liver function tests, blood pressure, heart rate and electrocardiogram monitoring

Those initiating diltiazem or verapamil should undergo liver function tests, blood pressure monitoring, heart rate assessment and electrocardiogram monitoring. For a dihydropyridine, monitoring blood pressure and heart rate is typically sufficient.

Answer: A. Constipation

Constipation is among the adverse effects reported with verapamil therapy, alongside fatigue, dyspepsia, gingival hyperplasia, hypotension and peripheral oedema. Paralytic ileus also appears among the severe reactions reported for this group.

Answer: A. Cluster headache

Verapamil is recommended as a first-line prophylactic agent to reduce headache severity and decrease episode frequency during a cluster period. It is also used off-label in hypertrophic cardiomyopathy where a beta blocker cannot be used.

Answer: B. Vitamin K epoxide reductase complex subunit 1

Warfarin competitively inhibits vitamin K epoxide reductase complex subunit 1, the enzyme that regenerates usable vitamin K. Depleting the active vitamin K supply starves the carboxylation step that clotting factor production depends on.

Answer: B. Factors II, VII, IX and X, plus proteins C and S

Vitamin K is the cofactor for the clotting factors II, VII, IX and X and also for the natural anticoagulants protein C and protein S. Reducing all six is what produces both the therapeutic effect and the transient prothrombotic window at the start.

Answer: B. Protein C falls faster than the clotting factors, so there is a brief prothrombotic period at the start

Protein C is a natural anticoagulant with a short survival in the circulation, so its level drops before the procoagulant factors do. That early imbalance is why cover with another anticoagulant is described during the first days of treatment.

Answer: C. CYP2C9

Warfarin is a racemic mixture whose S-enantiomer is several times more potent than the R-enantiomer, and S-warfarin is metabolised chiefly by CYP2C9. Interactions and genetic variants at CYP2C9 therefore have the largest effect on the achieved level of anticoagulation.

Answer: A. It falls, because rifampin induces the enzymes that metabolise warfarin

Rifampin is a cytochrome P450 inducer, so it speeds warfarin metabolism and the INR falls. The clinical risk here is thrombosis from under-anticoagulation rather than bleeding.

Answer: C. Acquired protein C deficiency causing microvascular thrombosis

Warfarin-induced skin necrosis follows the fall in protein C, a natural anticoagulant, which leaves small vessels in the skin prone to thrombosis. Risk is highest in people with an existing protein C or protein S deficiency.

Answer: C. The international normalized ratio, derived from the prothrombin time, is the preferred parameter

The INR is the preferred parameter for monitoring patients taking vitamin K antagonists. It expresses the prothrombin time as a ratio standardised for the potency of the laboratory's thromboplastin reagent, so results are comparable between laboratories.

Answer: B. Four-factor prothrombin complex concentrate together with intravenous vitamin K

Four-factor prothrombin complex concentrate corrects the factor deficit within minutes, and intravenous vitamin K is given with it so the correction is sustained once the concentrate is cleared. Fresh frozen plasma is described as a less effective alternative when the concentrate is unavailable.

Answer: B. Warfarin is almost entirely protein bound and cannot be removed by dialysis

Warfarin is about ninety-nine per cent protein bound and has a small volume of distribution, and the source states directly that it cannot be removed through haemodialysis. Management therefore relies on stopping the drug and giving vitamin K, with factor replacement where bleeding is serious.

Answer: B. By agonising central alpha-2 adrenergic and imidazoline receptors, reducing sympathetic outflow from the central nervous system

Clonidine is a central alpha-2 adrenergic and imidazoline receptor agonist. Acting in the nucleus tractus solitarii and reducing sympathetic outflow from the central nervous system produces a clinically significant fall in arterial blood pressure and in heart rate.

Answer: A. It is converted centrally to methyl norepinephrine, which reduces adrenergic outflow by alpha-2 agonism

Alpha-methyldopa is converted centrally to methyl norepinephrine, and that metabolite decreases adrenergic outflow from the central nervous system through alpha-2 agonistic action, lowering total peripheral resistance and systemic blood pressure.

Answer: B. Rebound hypertension, potentially amounting to a hypertensive crisis

Abrupt discontinuation may induce a hypertensive crisis, so clonidine must be tapered to avoid rebound hypertension. Rare cases of hypertensive encephalopathy, stroke and death have been reported, and the rebound can be reversed with oral clonidine or intravenous phentolamine.

Answer: C. The beta blocker is discontinued several days before the clonidine taper

Clonidine is tapered over several weeks and the beta blocker is discontinued several days earlier. Abrupt clonidine withdrawal in a patient on a beta blocker can precipitate rebound hypertension through unopposed sympathetic activity.

Answer: A. Coombs-positive haemolytic anaemia

Coombs-positive haemolytic anaemia sits among methyldopa's rare but clinically serious reactions, alongside a lupus-like syndrome, myocarditis, pancreatitis, hepatotoxicity and immune thrombocytopenia. Established direct Coombs-positive haemolytic anaemia is also a contraindication to the drug.

Answer: B. Because its alpha-2 agonistic activity does not affect cardiac output or renal blood flow

The alpha-2 agonistic activity that lowers total peripheral resistance does not affect cardiac output or renal blood flow, which is the stated reason the drug is useful in hypertensive patients with renal insufficiency.

Answer: B. Central alpha-2 agonists are listed as potentially inappropriate in older adults with hypertension because of the risk of bradycardia, hypotension and sedation

The American Geriatrics Society Beers Criteria list central alpha-2 agonists as potentially inappropriate for use in older adults with hypertension, and clonidine is not recommended as a first-line antihypertensive in that group because of bradycardia, hypotension and central nervous system effects such as sedation.

Answer: C. Supportive care, with atropine for bradycardia and fluids or vasopressors for hypotension

There is no specific antidote and treatment is primarily supportive: the airway is protected, bradycardia may be managed with atropine, and hypotension with intravenous fluids and vasopressors if needed. Dialysis is unlikely to increase elimination.

Answer: C. Dabigatran

Dabigatran, together with the acyl glucuronides it is converted into, competitively inhibits thrombin itself. The other three end in -xaban and act on factor Xa, which is one step earlier in the cascade.

Answer: B. It binds factor Xa itself and needs no cofactor, and it also inhibits clot-bound factor Xa

Rivaroxaban binds factor Xa directly and reversibly without any cofactor, and unlike the indirect inhibitors it acts on clot-bound as well as free factor Xa. Antithrombin is not involved in its antithrombotic activity.

Answer: B. The ester improves the very poor oral absorption of the active molecule and is hydrolysed after absorption

Dabigatran etexilate is the absorbed ester, which is then hydrolysed to dabigatran, the active moiety. The absolute bioavailability after oral administration remains only a few per cent, which is why the dosage forms are not interchangeable milligram for milligram.

Answer: D. Dabigatran

Dabigatran is eliminated predominantly in the urine, with renal clearance accounting for about four-fifths of total clearance. Apixaban is at the other end of the range, with roughly a quarter of the dose cleared renally.

Answer: A. It is avoided when creatinine clearance is very high as well as when it is very low

For stroke prevention in non-valvular atrial fibrillation, edoxaban is not recommended above a defined upper creatinine clearance because of increased ischaemic stroke risk, and it is also not used below a defined lower threshold. Creatinine clearance is assessed before starting.

Answer: C. Idarucizumab

Idarucizumab rapidly neutralises the anticoagulant effect of dabigatran and is named in the label for use when reversal is needed before emergency surgery or an urgent procedure in adults. Haemodialysis can also remove a substantial proportion of the drug.

Answer: B. Increased thrombotic risk after premature discontinuation, and spinal or epidural haematoma

Stopping an oral anticoagulant early, for any reason other than bleeding or completing the course, increases thrombotic risk. Separately, epidural or spinal haematoma can follow neuraxial anaesthesia or spinal puncture and may cause long-term or permanent paralysis.

Answer: C. Azole antifungals and HIV protease inhibitors

Azole antifungals such as ketoconazole and itraconazole, HIV protease inhibitors and some hepatitis C antivirals inhibit CYP3A4 and P-glycoprotein together, and these combinations are generally avoided or require dose reduction and close monitoring.

Answer: B. A mechanical heart valve

Current guidance recommends direct oral anticoagulants first for atrial fibrillation except in moderate-to-severe mitral stenosis and mechanical heart valves. Antiphospholipid syndrome and altered gastrointestinal anatomy are further named situations favouring a vitamin K antagonist.

Answer: A. Sodium reabsorption with water retention does not occur, and potassium is retained

Aldosterone binds its receptors at the distal tubules and collecting duct and causes sodium reabsorption with potassium secretion. Competitively blocking that receptor means the sodium reabsorption and water retention do not happen, and potassium is retained instead — the mechanism behind both the diuresis and the hyperkalaemia.

Answer: B. Spironolactone is a non-selective antagonist that also binds androgen and progesterone receptors

Spironolactone is a non-selective mineralocorticoid receptor antagonist that can also bind androgen and progesterone receptors, which is why men may experience gynaecomastia, loss of libido and general feminisation and women may experience menstrual irregularities. Eplerenone binds the mineralocorticoid receptor selectively relative to glucocorticoid, progesterone and androgen receptors.

Answer: C. RALES

The Randomized Aldactone Evaluation Study used spironolactone in NYHA class III to IV heart failure with an ejection fraction below 35%, and was stopped early on positive findings including a 30% relative risk reduction in all-cause mortality. EPHESUS studied eplerenone after myocardial infarction, PATHWAY-2 studied resistant hypertension, and FIDELIO-DKD studied finerenone in diabetic kidney disease.

Answer: B. Adults with chronic kidney disease associated with type 2 diabetes

Finerenone is a non-steroidal mineralocorticoid receptor antagonist indicated to reduce the risk of sustained estimated glomerular filtration rate decline, end-stage kidney disease, cardiovascular death, non-fatal myocardial infarction and hospitalisation for heart failure in adult patients with chronic kidney disease associated with type 2 diabetes.

Answer: C. Serum potassium above 5.5 mEq/L

Eplerenone is contraindicated in all patients with a serum potassium above 5.5 mEq/L at initiation, a creatinine clearance of 30 mL/min or less, or concomitant administration of strong CYP3A inhibitors. Previous gynaecomastia on spironolactone is in fact one of the reasons a clinician might choose eplerenone instead.

Answer: B. Finerenone is a CYP3A4 substrate, so exposure rises and the risk of adverse reactions increases

Finerenone is a CYP3A4 substrate. Concomitant use with a strong CYP3A4 inhibitor increases finerenone exposure, which may increase the risk of adverse reactions, so the combination is contraindicated and grapefruit intake is avoided.

Answer: B. Beta blockers, ACE inhibitors and angiotensin II receptor blockers

Cohort studies identified beta blockers, ACE inhibitors and angiotensin receptor blockers co-administered with spironolactone as risks for the development of severe hyperkalaemia. Advanced age, high-dose spironolactone, decreased renal function and type 2 diabetes add to that risk.

Answer: B. It binds the receptor and facilitates its lysosomal degradation

PCSK9 is secreted by hepatocytes into the plasma, binds LDL receptors and facilitates their degradation in the lysosome. Fewer surviving receptors means lower receptor density and reduced clearance of LDL cholesterol.

Answer: C. By preserving recycling of the LDL receptor back to the cell surface, increasing LDL uptake

With PCSK9 neutralised or not produced, the LDL receptor escapes lysosomal destruction and returns to the membrane. The resulting rise in receptor density increases uptake of LDL particles and lowers circulating cholesterol.

Answer: A. It is a small interfering RNA that silences PCSK9 gene expression rather than binding the circulating protein

Inclisiran is a synthetic double-stranded small interfering RNA directed against the messenger RNA of PCSK9, so it prevents the protein being made. The two antibodies instead bind PCSK9 that has already been secreted into plasma.

Answer: C. About 45% to 65%

LDL cholesterol falls by roughly 45% to 65%, achieved either as monotherapy or in combination with a statin. That is substantially more than a cholesterol absorption inhibitor achieves on its own.

Answer: B. FOURIER with evolocumab and ODYSSEY OUTCOMES with alirocumab

FOURIER studied evolocumab and ODYSSEY OUTCOMES studied alirocumab, and each reported a 15% reduction in its primary endpoint. IMPROVE-IT is the ezetimibe trial.

Answer: A. Injection-site reactions

Injection-site reactions are described for evolocumab, alirocumab and inclisiran alike. Nasopharyngitis and myalgia accompany the antibodies, while arthralgia is listed with inclisiran.

Answer: C. Enzyme elevations are uncommon and no instances of clinically apparent liver injury have been attributed to evolocumab or inclisiran

Enzyme elevations above three times the upper limit of normal occurred at rates similar to placebo with evolocumab, and inclisiran produced ALT elevations in under 1% of patients that were transient and asymptomatic. Both carry the lowest hepatotoxicity likelihood rating.

Answer: C. The aldosterone-sensitive distal nephron: late distal convoluted tubule, connecting tubules and collecting ducts

The target is the aldosterone-sensitive distal nephron. Because that segment accounts for the reabsorption of only about 3% of the filtered sodium load, the diuretic effect is small and the potassium effect is what makes the class useful.

Answer: A. Amiloride blocks the epithelial sodium channel directly and works independently of aldosterone

Amiloride binds epithelial sodium channels in the principal cells and suppresses them directly, without depending on aldosterone. Receptor antagonists instead suppress the aldosterone-induced proteins that increase production, redistribution and activation of those channels.

Answer: B. Reduced sodium entry lessens the apical membrane depolarisation that drives potassium secretion

Sodium entry through the channel is what depolarises the apical membrane and creates the gradient for potassium secretion. Blocking it therefore reduces secretion not only of potassium but also of hydrogen, calcium and magnesium ions.

Answer: B. Patients with advanced renal failure or chronic kidney disease, particularly below 30 mL/min/1.73 m2

Advanced renal impairment is the stated contraindication, and the risk is described as particularly relevant below a filtration rate of 30 mL/min/1.73 m2. Hypokalaemia from another diuretic, aldosteronism and Liddle syndrome are all reasons the class is used, not withheld.

Answer: C. Amiloride

Liddle syndrome is a disorder of the epithelial sodium channel itself, so direct channel blockade addresses the defect. Mineralocorticoid receptor antagonists act one step upstream and are the rational choice in aldosterone excess instead.

Answer: B. Crystalline deposition in the renal tubules with nephrolithiasis and interstitial nephritis

Triamterene is linked to nephrolithiasis in patients with a stone history, to urolithiasis, to crystalline deposition in renal tubules causing acute renal failure, and to drug-induced interstitial nephritis. These are agent-specific rather than class effects.

Answer: A. A potassium-sparing diuretic with a renin-angiotensin system inhibitor, beta blocker, NSAID or aliskiren

Each of those agents causes some degree of potassium retention on its own, so adding a potassium-sparing diuretic can produce hyperkalaemia. Pairing with a thiazide or a loop diuretic is the standard use of the class, since those agents waste potassium.

Answer: B. The funny current I(f), carried by HCN channels in the sinoatrial node

Ivabradine selectively blocks the funny current, I(f), by inhibiting hyperpolarisation-activated cyclic nucleotide-gated channels in the sinoatrial node. Inhibiting that current reduces the rate of phase 4 pacemaker depolarisation and so lowers the heart rate.

Answer: A. It reduces heart rate without affecting contraction, relaxation or ventricular repolarisation

Ivabradine reduces heart rate but does not affect myocardial contraction, relaxation or ventricular repolarisation. That is why it can be added when a patient with heart failure remains tachycardic on the maximum beta blocker dose they can tolerate.

Answer: C. Phosphenes, brief luminous visual disturbances

Phosphenes are the distinctive ivabradine visual phenomenon. In the SHIFT trial they occurred in 3% of patients taking ivabradine compared with less than 1% of those on placebo. Corneal microdeposits point to amiodarone and xanthopsia to digoxin.

Answer: C. By inhibiting the late inward sodium current, which lowers intracellular calcium and wall tension

Ranolazine inhibits the late inward sodium current in ischaemic cardiac myocytes. Intracellular sodium falls, so less calcium enters through the sodium-calcium exchanger, ventricular wall tension decreases and oxygen consumption falls — without significantly affecting blood pressure or heart rate.

Answer: A. Inhibition of mitochondrial long-chain 3-ketoacyl coenzyme A thiolase, shifting metabolism towards glucose oxidation

Trimetazidine inhibits mitochondrial long-chain 3-ketoacyl coenzyme A thiolase, moving cardiac energy production away from fatty acid oxidation towards glucose oxidation. Glucose metabolism is oxygen-sparing, yielding about 15% more ATP per unit of oxygen, and the effect occurs with no detectable chronotropic or vasomotor change.

Answer: B. Parkinson disease and similar movement disorders

Some patients experience extrapyramidal complications with trimetazidine, which makes it unsuitable in Parkinson disease. Caution is also advised in older patients and in those with moderate renal impairment, who need a reduced amount.

Answer: B. Because ivabradine undergoes extensive CYP3A4-mediated metabolism, so inhibition raises its exposure

Ivabradine undergoes extensive hepatic metabolism by CYP3A4-mediated oxidation, so a potent inhibitor of that enzyme raises drug exposure and the associated bradycardia risk. Strong inhibitors named include azole antifungals, macrolides, HIV protease inhibitors, verapamil and diltiazem.

Answer: C. As a metabolically dependent potassium channel opener

Nicorandil is listed among metabolically dependent potassium channel openers. It opens ATP-sensitive potassium channels, shortening action potential recovery, refractoriness and repolarisation reserve in cardiomyocytes other than sinoatrial node cells, and shortening the QT interval.

Answer: B. Because neprilysin also degrades angiotensin II, so inhibiting it causes angiotensin II to accumulate

Neprilysin breaks down angiotensin II as well as natriuretic peptides. Inhibiting the enzyme therefore causes an accumulation of angiotensin II, so a neprilysin inhibitor cannot be used alone and is combined with an angiotensin receptor blocker to block the effect of that excess.

Answer: C. 36 hours

A 36-hour washout is required when switching between an ACE inhibitor and sacubitril-valsartan, and the labelling states the drug must not be administered within 36 hours of switching from or to an ACE inhibitor. The reason is bradykinin: both drugs reduce its breakdown, and overlapping them raises the risk of angio-oedema.

Answer: B. It prevents breakdown of natriuretic peptides, prolonging vasodilation, natriuresis and diuresis

The enzyme neprilysin degrades natriuretic peptides. Blocking it prevents that breakdown and prolongs their favourable effects — vasodilation, natriuresis and diuresis, with lower blood pressure, lower sympathetic tone and reduced aldosterone. That system functions antagonistically to the renin-angiotensin-aldosterone system.

Answer: A. A history of angio-oedema related to previous ACE inhibitor or ARB therapy

The drug is contraindicated in patients with hypersensitivity to any component, in patients with a history of angio-oedema related to previous ACE inhibitor or ARB therapy, with concomitant use of an ACE inhibitor, and with concomitant aliskiren in patients with diabetes. Beta blockers are in fact part of the standard therapy it is used alongside.

Answer: B. More hypotension, but lower risk of raised potassium or creatinine and less cough

Compared with enalapril, sacubitril-valsartan was associated with a higher incidence of hypotension and symptomatic hypotension, and a lower risk of elevated serum potassium or serum creatinine as well as a lower risk of cough. More patients experienced angio-oedema in the sacubitril-valsartan arm, although that difference was not statistically significant.

Answer: B. Patients should be able to tolerate an ACE inhibitor or an ARB before it is initiated

The guideline position is that patients should be able to tolerate an ACE inhibitor or an ARB before sacubitril-valsartan is initiated, and the drug is then used instead of that agent alongside other standard heart failure treatments such as a beta blocker or an aldosterone antagonist. Previous angio-oedema on an ACE inhibitor or ARB is a contraindication, not an indication.

Answer: B. Both reduce bradykinin breakdown, so kinin accumulation is compounded

Bradykinin is another substance broken down by neprilysin, so inhibiting neprilysin causes bradykinin to build up. An ACE inhibitor blocks a second route of bradykinin degradation. Using them together, or too close in time, therefore compounds kinin accumulation and increases the risk of angio-oedema.

Answer: B. Peroxisome proliferator-activated receptor alpha

Fibrates activate transcription factors for peroxisome proliferator-activated receptors, and PPAR-alpha activation downregulates apolipoprotein C-III. The downstream result is increased lipoprotein lipase-mediated lipolysis of triglyceride-rich particles.

Answer: C. Hypertriglyceridaemia

Fibrates are primarily used to lower triglycerides, and severe hypertriglyceridaemia of Fredrickson types IV and V is among their approved indications. Statins remain the first-line drugs where LDL cholesterol is the problem.

Answer: A. Because hepatic production of apolipoprotein A-I and A-II is upregulated

Fibrates increase HDL levels by upregulating hepatic production of apolipoprotein A-I and apolipoprotein A-II, which are the principal structural apolipoproteins of HDL.

Answer: B. It inhibits the OATP1B1 transporter and represses CYP2C8, raising statin exposure, and has proved unsafe in this combination

Gemfibrozil inhibits OATP1B1 and so increases exposure to substrates of that transporter, and it also represses CYP2C8. It has proved unsafe in combination with a statin, whereas bezafibrate and fenofibrate remain options.

Answer: A. Active gallbladder disease

Active gallbladder disease is a contraindication because PPAR-alpha-mediated downregulation of bile acids increases gallstone risk. Active liver disease and severe renal dysfunction are the other recorded contraindications.

Answer: C. Clofibrate, largely because of concerns about an increased risk of cancer

Clofibrate has been withdrawn from use, largely over concerns regarding an increased risk of cancer. Gemfibrozil and fenofibrate remain the fibrates used in the United States.

Answer: B. Coagulation testing, with prothrombin time and INR followed frequently

Fibrates interact with coumarin anticoagulants, and frequent monitoring of prothrombin time and INR is required. With gemfibrozil specifically, reduction of the anticoagulant dose and monitoring of the coagulation cascade is described.

Answer: B. By binding antithrombin III and greatly enhancing its inactivation of thrombin and factor Xa

Heparin binds antithrombin III and induces a conformational change that greatly increases its ability to inactivate clotting factors, most importantly thrombin and factor Xa. The drug itself has no direct action on those enzymes.

Answer: B. Its chain is too short to hold antithrombin and thrombin together simultaneously

Inhibiting thrombin requires the heparin molecule to bridge antithrombin and thrombin on the same chain, which needs a long saccharide chain. Factor Xa inhibition requires only the antithrombin binding sequence, so a shorter chain retains it.

Answer: C. Fondaparinux

Fondaparinux consists of only the five sugars that make up the antithrombin binding sequence. Because it is too small to form the complexes that provoke the immune response, it does not cause the reaction and does not react with heparin-induced antibodies.

Answer: B. IgG antibodies against a heparin-platelet factor 4 complex that activate platelets via the Fc receptor

Platelet factor 4 binds heparin with high affinity, and IgG raised against that complex engages the platelet Fc receptor. Activated platelets release more platelet factor 4 and prothrombotic mediators, driving a self-amplifying hypercoagulable cycle.

Answer: B. Stop all forms of heparin and start a non-heparin anticoagulant

All heparin exposure is stopped, including flushes and coated catheters, and an alternative anticoagulant is started because the prothrombotic state persists for weeks. Warfarin alone is not appropriate acutely, since falling protein C risks skin necrosis.

Answer: C. Serotonin release assay

The immunoassay detects antibodies and is sensitive but poorly specific, so it is best at ruling the diagnosis out. The serotonin release assay measures whether the patient's antibodies actually activate platelets in the presence of heparin, and is the gold standard for confirmation.

Answer: B. It neutralises unfractionated heparin rapidly by forming an inactive salt complex

Protamine is a positively charged peptide that forms an inactive salt aggregate with the strongly negatively charged heparin molecule, neutralising it within about five minutes. Reversal of low-molecular-weight heparin is partial only, and protamine carries a real risk of anaphylaxis and pulmonary hypertension.

Answer: B. It does not bind platelet factor 4 and so does not cross-react with the causative antibodies

Bivalirudin binds thrombin at its catalytic site and anion-binding exosite and does not bind platelet factor 4, so there is no cross-reactivity with heparin-induced antibodies. Argatroban is likewise a direct, non-immune inhibitor and is licensed for this setting.

Answer: A. Antithrombin deficiency or consumption, so-called heparin resistance

Heparin acts only through antithrombin, so inflammation, major thrombosis, malignancy, the postoperative state and inherited antithrombin deficiency all blunt the response. In these situations anti-factor Xa monitoring is used because the activated partial thromboplastin time becomes unreliable.

Answer: B. Cleavage of plasminogen into plasmin

All thrombolytic agents are serine proteases that convert plasminogen into plasmin, which is the enzyme that actually degrades fibrin. This is why the class is also called the plasminogen activators.

Answer: D. Streptokinase

Streptokinase is the principal non-fibrin-specific agent: it activates plasminogen without needing fibrin binding, so fibrinolysis occurs throughout the circulation. The three recombinant tissue plasminogen activators preferentially activate fibrin-bound plasminogen.

Answer: B. Three point mutations prolong its half-life and it resists plasminogen activator inhibitor-1

Tenecteplase is a bioengineered variant of tissue plasminogen activator with three amino acid substitutions that slow its clearance and increase resistance to the endogenous inhibitor, giving it a substantially longer plasma half-life than alteplase.

Answer: B. It lacks the kringle-1 domain, which slows clearance and weakens fibrin binding

Reteplase is an unglycosylated deletion variant lacking kringle-1. Slower plasma clearance supports bolus administration, and weaker fibrin binding lets it diffuse into the clot rather than acting mainly at the surface.

Answer: A. Streptokinase must first form a complex with plasminogen, whereas urokinase converts plasminogen directly

Streptokinase binds free circulating plasminogen and the resulting complex then activates further plasminogen. Urokinase is a direct activator and, being non-antigenic, can be given repeatedly, unlike the bacterial streptokinase.

Answer: C. Recent intracranial haemorrhage

Recent intracranial haemorrhage is an absolute contraindication, alongside a structural cerebral vascular lesion, ischaemic stroke within the preceding months, possible aortic dissection, active bleeding or a bleeding tendency, recent significant head or facial trauma, recent intracranial or spinal surgery, and severe uncontrolled hypertension. Menstruation is explicitly excluded from the active-bleeding criterion.

Answer: A. Orolingual angio-oedema, most frequent with alteplase and commoner with an ACE inhibitor

Orolingual angio-oedema occurs most frequently with alteplase, particularly in patients also receiving an angiotensin-converting enzyme inhibitor, and it can obstruct the airway, so airway readiness is part of preparing for treatment.

Answer: C. Aminocaproic acid

Aminocaproic acid is an antifibrinolytic that inhibits plasmin-mediated fibrin degradation. It is reserved for severe bleeding because suppressing endogenous fibrinolysis raises thrombotic risk, and blood products such as cryoprecipitate and fresh frozen plasma are used to replace fibrinogen and clotting factors.

Answer: C. It declines, so the benefit is greatest when treatment starts early

Benefit is significant when treatment begins early after onset and declines with delay. This underlies both the treatment window in acute ischaemic stroke and the emphasis on minimising door-to-needle time in myocardial infarction.