Analgesia and anaesthesia: Practice MCQs

42 practice questions with answers and explanations across 7 drug classes. All practice questions · Analgesia and anaesthesia study guides · Download as flashcards (CSV)

Gabapentinoids and neuropathic pain agents

Revise the Gabapentinoids and neuropathic pain agents guide

  1. What is the shared molecular mechanism of gabapentin and pregabalin?

    1. Both block presynaptic voltage-gated calcium channels by binding the alpha-2-delta subunit, reducing release of excitatory neurotransmitters
    2. Both are GABA-A receptor agonists, directly mimicking GABA
    3. Both block voltage-gated sodium channels, similar to local anaesthetics
    4. Both act as mu-opioid receptor partial agonists
    Show answer

    Answer: A. Both block presynaptic voltage-gated calcium channels by binding the alpha-2-delta subunit, reducing release of excitatory neurotransmitters

    Despite the name 'gabapentinoid' suggesting a GABA mechanism, both drugs act by binding the alpha-2-delta subunit of presynaptic voltage-gated calcium channels, which reduces calcium influx and decreases release of excitatory neurotransmitters — they do not directly act at GABA receptors.

  2. Under what circumstance does the strongest evidence for gabapentinoid-related respiratory depression apply?

    1. Only when the drug is taken alone by a young, healthy adult
    2. When combined with opioids or other CNS depressants, or in patients with underlying respiratory impairment such as COPD
    3. Only in patients under 18 years of age
    4. Gabapentinoids have never been associated with respiratory depression
    Show answer

    Answer: B. When combined with opioids or other CNS depressants, or in patients with underlying respiratory impairment such as COPD

    Postmarketing reports of life-threatening or fatal respiratory depression with gabapentinoids are concentrated in patients also taking opioids or other CNS depressants, or those with underlying respiratory impairment — the FDA's warning specifically names these risk factors.

  3. Which FDA-approved indication belongs to pregabalin but not gabapentin?

    1. Postherpetic neuralgia
    2. Fibromyalgia
    3. Adjunctive therapy for partial-onset seizures
    4. Neither drug has any FDA-approved indication
    Show answer

    Answer: B. Fibromyalgia

    Pregabalin carries FDA approval for fibromyalgia (as well as diabetic peripheral neuropathy and spinal cord injury pain) that gabapentin does not share, even though both drugs are approved for postherpetic neuralgia and used for seizure-related indications.

  4. Why does pregabalin's label specifically direct tapering over at least one week when stopping the drug?

    1. Because tapering has no clinical basis and is a purely precautionary instruction
    2. Because abrupt discontinuation is associated with a withdrawal syndrome including insomnia, nausea, headache, anxiety, hyperhidrosis and diarrhoea
    3. Because the drug is not eliminated from the body unless tapered
    4. Because tapering prevents an allergic skin reaction
    Show answer

    Answer: B. Because abrupt discontinuation is associated with a withdrawal syndrome including insomnia, nausea, headache, anxiety, hyperhidrosis and diarrhoea

    Pregabalin's prescribing information documents insomnia, nausea, headache, anxiety, hyperhidrosis and diarrhoea following abrupt discontinuation. Tapering over a minimum of one week is the specific, labelled way to reduce this withdrawal syndrome.

  5. What regulatory fact reflects documented misuse potential in this drug class?

    1. Neither gabapentin nor pregabalin has ever been subject to any controlled-substance scheduling
    2. Pregabalin is a federal Schedule V controlled substance, and several US states have separately reclassified gabapentin as Schedule V
    3. Both drugs are Schedule II, the same as most opioids
    4. Scheduling applies only to the paediatric formulations of these drugs
    Show answer

    Answer: B. Pregabalin is a federal Schedule V controlled substance, and several US states have separately reclassified gabapentin as Schedule V

    Pregabalin is federally classified as a Schedule V controlled substance. Gabapentin, while not federally scheduled, has been independently reclassified as Schedule V by several US states in response to documented misuse, particularly alongside opioids.

General anaesthetics

Revise the General anaesthetics guide

  1. What does minimum alveolar concentration (MAC) actually measure?

    1. The blood concentration at which 50% of patients become unconscious
    2. The alveolar concentration of an inhaled anaesthetic at which 50% of people do not move in response to a noxious stimulus
    3. The maximum safe concentration before respiratory arrest occurs
    4. The concentration required for complete amnesia in all patients
    Show answer

    Answer: B. The alveolar concentration of an inhaled anaesthetic at which 50% of people do not move in response to a noxious stimulus

    MAC is specifically defined as the minimum alveolar concentration at which 50% of people do not move in response to a noxious stimulus. It is a potency and surgical-immobility benchmark, used to compare inhalational agents, not a direct measure of unconsciousness or amnesia.

  2. How does ketamine's mechanism differ from that of propofol?

    1. Both work identically through GABA-A receptor enhancement
    2. Ketamine acts through noncompetitive NMDA receptor antagonism producing dissociative anaesthesia, while propofol acts by prolonging GABA-A chloride channel opening
    3. Ketamine blocks voltage-gated sodium channels, exactly like a local anaesthetic
    4. Propofol works through NMDA antagonism and ketamine through GABA enhancement — the reverse of the true mechanisms
    Show answer

    Answer: B. Ketamine acts through noncompetitive NMDA receptor antagonism producing dissociative anaesthesia, while propofol acts by prolonging GABA-A chloride channel opening

    Propofol binds GABA-A receptors and prolongs chloride-channel opening, hyperpolarising neurons. Ketamine instead works mainly through noncompetitive NMDA receptor antagonism, producing a dissociative anaesthetic state with relatively preserved airway reflexes and haemodynamics.

  3. Why is etomidate no longer given as a continuous infusion?

    1. It causes unacceptable cardiovascular depression with prolonged use
    2. It causes dose-dependent inhibition of 11-beta-hydroxylase, suppressing cortisol synthesis, and sustained infusion risks prolonged adrenal suppression
    3. It has too short a duration of action to be infused
    4. It causes malignant hyperthermia when infused continuously
    Show answer

    Answer: B. It causes dose-dependent inhibition of 11-beta-hydroxylase, suppressing cortisol synthesis, and sustained infusion risks prolonged adrenal suppression

    Even a single etomidate bolus measurably suppresses cortisol synthesis via 11-beta-hydroxylase inhibition, an effect lasting 6 to 12 hours. Continuous infusion was abandoned because sustained suppression of the adrenal stress response is a genuine safety concern.

  4. What is the underlying defect responsible for malignant hyperthermia?

    1. An acquired liver enzyme deficiency that prevents anaesthetic metabolism
    2. A hereditary defect in the ryanodine receptor causing uncontrolled calcium release in skeletal muscle in response to a triggering agent
    3. An allergic IgE-mediated reaction to inhalational anaesthetic vapour
    4. Excess circulating cortisol triggered by surgical stress
    Show answer

    Answer: B. A hereditary defect in the ryanodine receptor causing uncontrolled calcium release in skeletal muscle in response to a triggering agent

    Malignant hyperthermia is a hereditary pharmacogenetic disorder in which a defective ryanodine receptor in the skeletal muscle sarcoplasmic reticulum releases calcium uncontrollably when triggered by a halogenated anaesthetic or succinylcholine, producing a hypermetabolic crisis. Dantrolene treats it by directly antagonising that receptor.

  5. What best describes propofol infusion syndrome?

    1. An immediate anaphylactic reaction occurring within minutes of the first propofol dose
    2. A rare complication, typically appearing within about four days of prolonged high-dose propofol infusion, involving mitochondrial dysfunction and cardiac/skeletal muscle injury, with reported mortality of roughly 18 to 32%
    3. A benign, self-limiting rash seen with any propofol exposure
    4. A withdrawal syndrome occurring after propofol is stopped
    Show answer

    Answer: B. A rare complication, typically appearing within about four days of prolonged high-dose propofol infusion, involving mitochondrial dysfunction and cardiac/skeletal muscle injury, with reported mortality of roughly 18 to 32%

    Propofol infusion syndrome typically develops within about four days of prolonged high-dose administration. Its proposed mechanism involves impaired mitochondrial fatty-acid metabolism and an energy-demand mismatch leading to cardiac and skeletal muscle necrosis, and reported mortality is substantial at roughly 18 to 32%.

  6. Why is nitrous oxide avoided in bowel surgery, craniotomy and intraocular procedures?

    1. It is directly neurotoxic to those tissues
    2. Its high solubility lets it diffuse into and expand closed air-containing spaces faster than nitrogen can leave them, raising pressure in those spaces
    3. It causes malignant hyperthermia specifically in those procedures
    4. It has no relevant contraindication in these settings
    Show answer

    Answer: B. Its high solubility lets it diffuse into and expand closed air-containing spaces faster than nitrogen can leave them, raising pressure in those spaces

    Nitrous oxide is highly soluble and diffuses into closed gas-filled spaces (bowel lumen, intracranial or intraocular air) faster than the nitrogen already there can be washed out, expanding those spaces and raising pressure — a mechanical rather than toxic hazard.

NSAIDs, including COX-2 selective agents

Revise the NSAIDs, including COX-2 selective agents guide

  1. What is the core enzymatic mechanism shared by all NSAIDs?

    1. Inhibition of lipoxygenase, blocking leukotriene synthesis
    2. Inhibition of cyclo-oxygenase (COX-1 and/or COX-2), reducing prostaglandin, prostacyclin and thromboxane synthesis from arachidonic acid
    3. Blockade of voltage-gated sodium channels in peripheral nerves
    4. Antagonism of the mu-opioid receptor
    Show answer

    Answer: B. Inhibition of cyclo-oxygenase (COX-1 and/or COX-2), reducing prostaglandin, prostacyclin and thromboxane synthesis from arachidonic acid

    NSAIDs inhibit cyclo-oxygenase, the enzyme that converts arachidonic acid into prostaglandins, thromboxanes and prostacyclin. Whether an agent inhibits COX-1, COX-2 or both determines its specific benefit and risk profile.

  2. Why does inhibiting COX-1 specifically raise gastrointestinal bleeding risk?

    1. COX-1 produces the acid that neutralises stomach protection
    2. COX-1 is constitutively expressed and its prostaglandin products maintain gastric mucosal blood flow and mucous secretion; blocking it removes that protection
    3. COX-1 has no role in the gastrointestinal tract
    4. COX-1 inhibition increases gastric acid production directly
    Show answer

    Answer: B. COX-1 is constitutively expressed and its prostaglandin products maintain gastric mucosal blood flow and mucous secretion; blocking it removes that protection

    COX-1-derived prostaglandins such as PGE2 and PGI2 maintain gastric mucous secretion and mucosal blood flow. Removing that constitutive protection is what makes non-selective COX-1 inhibition ulcerogenic, independent of any anti-inflammatory action.

  3. Why is celecoxib still contraindicated in the setting of coronary artery bypass graft (CABG) surgery despite being COX-2 selective?

    1. Celecoxib has no cardiovascular risk and the contraindication is outdated
    2. COX-2 selective inhibition still carries a boxed warning for serious cardiovascular thrombotic events, and celecoxib's label specifically contraindicates it in the CABG setting
    3. Celecoxib causes excessive bleeding through irreversible COX-1 inhibition, exactly like aspirin
    4. Celecoxib is metabolised only by the kidney, which fails during CABG
    Show answer

    Answer: B. COX-2 selective inhibition still carries a boxed warning for serious cardiovascular thrombotic events, and celecoxib's label specifically contraindicates it in the CABG setting

    COX-2 selectivity reduces GI risk relative to non-selective NSAIDs but does not remove cardiovascular thrombotic risk. Celecoxib's FDA label carries the same class-wide cardiovascular boxed warning and specifically contraindicates use in the CABG surgical setting.

  4. What makes aspirin's antiplatelet effect different from that of ibuprofen?

    1. Aspirin has no effect on platelets; only ibuprofen does
    2. Aspirin irreversibly acetylates COX, so its effect lasts the roughly week-long lifespan of the platelet; ibuprofen's inhibition is reversible and tracks plasma concentration
    3. Ibuprofen's antiplatelet effect is permanent while aspirin's is reversible
    4. Both drugs have an identical, reversible antiplatelet duration
    Show answer

    Answer: B. Aspirin irreversibly acetylates COX, so its effect lasts the roughly week-long lifespan of the platelet; ibuprofen's inhibition is reversible and tracks plasma concentration

    Aspirin irreversibly binds cyclo-oxygenase, so a platelet exposed to aspirin cannot regenerate the enzyme for the rest of its roughly seven-to-ten-day lifespan. Other NSAIDs inhibit COX reversibly, so their antiplatelet effect disappears as the drug is cleared.

  5. A patient taking an ACE inhibitor and a diuretic is started on an NSAID and develops acute kidney injury within days. What is this interaction called, and why does it happen?

    1. The 'triple whammy' — the NSAID removes prostaglandin-dependent afferent arteriolar dilation while the ACE inhibitor and diuretic remove the other renal compensatory mechanisms
    2. Serotonin syndrome, from combined serotonergic activity
    3. The 'double cover' effect, from combined COX-1 and COX-2 inhibition alone
    4. This combination has no recognised interaction risk
    Show answer

    Answer: A. The 'triple whammy' — the NSAID removes prostaglandin-dependent afferent arteriolar dilation while the ACE inhibitor and diuretic remove the other renal compensatory mechanisms

    This is the named 'triple whammy': an NSAID blunts prostaglandin-mediated afferent arteriolar dilation, while an ACE inhibitor/ARB and a diuretic remove other renal protective mechanisms, together raising acute kidney injury risk sharply and quickly.

  6. Why does the FDA boxed warning emphasise that serious GI and cardiovascular NSAID events can occur 'without warning symptoms'?

    1. Because these events are always preceded by clear abdominal pain
    2. Because a patient can be at risk of a fatal event without any preceding symptom to prompt a clinical visit, so risk assessment cannot rely on symptoms alone
    3. Because the warning applies only to patients already hospitalised
    4. Because NSAIDs cause symptoms only after the event has occurred
    Show answer

    Answer: B. Because a patient can be at risk of a fatal event without any preceding symptom to prompt a clinical visit, so risk assessment cannot rely on symptoms alone

    The label states these serious events can occur at any time during use and without warning symptoms, which is precisely why risk factors, duration of use and dose are assessed proactively rather than waiting for symptoms to appear.

Opioid analgesics

Revise the Opioid analgesics guide

  1. By what dual mechanism do opioids produce analgesia at the mu receptor?

    1. They block postsynaptic sodium channels and open presynaptic chloride channels
    2. They block presynaptic calcium channels, reducing neurotransmitter release, and open postsynaptic potassium channels, hyperpolarising the neuron
    3. They act purely postsynaptically by blocking NMDA receptors
    4. They inhibit cyclooxygenase presynaptically to reduce prostaglandin release
    Show answer

    Answer: B. They block presynaptic calcium channels, reducing neurotransmitter release, and open postsynaptic potassium channels, hyperpolarising the neuron

    Opioids act presynaptically by blocking calcium channels on nociceptive afferents, reducing release of substance P and glutamate, and postsynaptically by opening potassium channels, which hyperpolarises the cell membrane. Both actions reduce pain signal transmission.

  2. Why is codeine contraindicated in children younger than 12 years?

    1. Codeine is not absorbed orally in children
    2. Codeine directly damages the paediatric respiratory centre regardless of metabolism
    3. CYP2D6 ultra-rapid metabolisers convert codeine to morphine unusually fast and completely, producing life-threatening or fatal respiratory depression
    4. Children lack mu-opioid receptors until puberty
    Show answer

    Answer: C. CYP2D6 ultra-rapid metabolisers convert codeine to morphine unusually fast and completely, producing life-threatening or fatal respiratory depression

    Codeine's analgesic effect depends on CYP2D6 converting it to morphine. Ultra-rapid metabolisers — whose prevalence varies by ethnicity — produce abnormally high morphine levels even at labelled doses, which is why the FDA label contraindicates codeine under 12 and after tonsillectomy/adenoidectomy under 18.

  3. According to the 2022 CDC opioid prescribing guideline, what is the preferred first approach to subacute and chronic pain?

    1. Immediate-release opioids at the lowest dose for the shortest duration
    2. Maximising nonpharmacologic and nonopioid pharmacologic therapies, since these are preferred for subacute and chronic pain
    3. Extended-release/long-acting opioids started early to prevent dose escalation
    4. Routine co-prescription of benzodiazepines to manage anxiety around chronic pain
    Show answer

    Answer: B. Maximising nonpharmacologic and nonopioid pharmacologic therapies, since these are preferred for subacute and chronic pain

    The guideline states nonopioid therapies are preferred for subacute and chronic pain, and clinicians should maximise nonpharmacologic and nonopioid pharmacologic therapies before or alongside any opioid use.

  4. What distinguishes methadone's boxed warning from that of most other opioids?

    1. Methadone alone carries a warning for gastrointestinal perforation
    2. Methadone alone carries a warning for life-threatening QT prolongation and torsades de pointes, in addition to the class-wide respiratory depression warning
    3. Methadone is the only opioid with no addiction potential
    4. Methadone alone requires no monitoring for respiratory depression
    Show answer

    Answer: B. Methadone alone carries a warning for life-threatening QT prolongation and torsades de pointes, in addition to the class-wide respiratory depression warning

    Methadone's label adds a specific boxed warning for QT interval prolongation and torsades de pointes, reported more often with doses above 200 mg/day, on top of the respiratory depression and addiction warnings shared with the rest of the class.

  5. A patient is reversed from an apparent long-acting opioid overdose with naloxone and initially wakes. Why does the care team keep monitoring rather than discharge the patient?

    1. Naloxone permanently blocks the mu receptor for 24 hours, so no further risk exists
    2. Naloxone's effect lasts only about 30 to 60 minutes, so a long-acting or large-quantity opioid can outlast a single dose and re-sedation can follow
    3. Naloxone itself causes delayed respiratory depression
    4. Monitoring is required only for children, never for adults
    Show answer

    Answer: B. Naloxone's effect lasts only about 30 to 60 minutes, so a long-acting or large-quantity opioid can outlast a single dose and re-sedation can follow

    Naloxone is a short-acting competitive mu-antagonist. Because its action lasts only 30 to 60 minutes, an opioid with a longer duration of action can re-assert its effect once naloxone wears off, so repeated dosing and observation are standard practice.

  6. Why does the CDC guideline advise against detoxification alone for opioid use disorder?

    1. Detoxification alone is more expensive than medication treatment
    2. Detoxification alone removes tolerance without treating the underlying disorder, raising the risk of fatal overdose on relapse
    3. Detoxification alone is illegal in the United States
    4. Detoxification alone works only for methadone, not other opioids
    Show answer

    Answer: B. Detoxification alone removes tolerance without treating the underlying disorder, raising the risk of fatal overdose on relapse

    The guideline recommends offering or arranging evidence-based medication treatment for opioid use disorder and states that detoxification on its own, without medications, is not recommended because of the overdose risk it carries.

  7. Which statement about concurrent benzodiazepine and opioid use is correct?

    1. It is safe as long as the benzodiazepine is short-acting
    2. It carries an FDA boxed warning and CDC guidance urging particular caution, because of profound sedation, respiratory depression, coma and death
    3. It is only dangerous in patients over 65
    4. It is recommended as standard practice for anxious patients starting opioid therapy
    Show answer

    Answer: B. It carries an FDA boxed warning and CDC guidance urging particular caution, because of profound sedation, respiratory depression, coma and death

    Both the opioid boxed warning and the CDC guideline flag concurrent benzodiazepine and opioid (or other CNS depressant) use as a specific, serious risk requiring particular caution and a documented risk-benefit discussion, not routine co-prescribing.

Local anaesthetics

Revise the Local anaesthetics guide

  1. What is the core mechanism by which local anaesthetics prevent nerve conduction?

    1. They block voltage-gated sodium channels, preventing sodium influx and action potential generation, preferentially in frequently firing channels
    2. They open potassium channels to hyperpolarise the nerve permanently
    3. They inhibit acetylcholinesterase at the neuromuscular junction
    4. They antagonise NMDA receptors in the peripheral nerve
    Show answer

    Answer: A. They block voltage-gated sodium channels, preventing sodium influx and action potential generation, preferentially in frequently firing channels

    Local anaesthetics block voltage-gated sodium channels, preventing sodium influx and thus action potential generation. The block is use-dependent, meaning channels that fire more frequently — such as those carrying pain signals — are blocked preferentially.

  2. Why is bupivacaine considered disproportionately more cardiotoxic than lidocaine?

    1. Bupivacaine is metabolised entirely by the kidney, unlike lidocaine
    2. Bupivacaine has high affinity for and slow dissociation from cardiac sodium channels, allowing block to accumulate between heartbeats, unlike the more rapidly dissociating lidocaine
    3. Bupivacaine has no effect on cardiac sodium channels at all
    4. Lidocaine is actually more cardiotoxic than bupivacaine
    Show answer

    Answer: B. Bupivacaine has high affinity for and slow dissociation from cardiac sodium channels, allowing block to accumulate between heartbeats, unlike the more rapidly dissociating lidocaine

    Bupivacaine binds cardiac sodium channels with high affinity and dissociates slowly, so a meaningful fraction of channels stays blocked between action potentials — an accumulating effect that the more rapidly dissociating lidocaine does not share, explaining why lidocaine toxicity is predominantly neurologic while bupivacaine toxicity is predominantly cardiac.

  3. What is the typical clinical sequence of local anaesthetic systemic toxicity (LAST)?

    1. Cardiovascular collapse occurs first, followed later by CNS symptoms
    2. CNS symptoms (metallic taste, circumoral numbness, agitation, seizures) typically precede cardiovascular symptoms (hypotension, dysrhythmia, collapse)
    3. Only cardiovascular symptoms occur; CNS symptoms are not part of LAST
    4. Symptoms are entirely unpredictable and follow no typical pattern
    Show answer

    Answer: B. CNS symptoms (metallic taste, circumoral numbness, agitation, seizures) typically precede cardiovascular symptoms (hypotension, dysrhythmia, collapse)

    LAST typically follows a predictable sequence: CNS manifestations appear first, followed by cardiovascular manifestations. Recognising the early CNS phase is what allows intervention before cardiovascular collapse develops.

  4. What is the first-line treatment for local anaesthetic systemic toxicity?

    1. High-dose intravenous naloxone
    2. 20% intravenous lipid emulsion, given as a bolus followed by a continuous infusion
    3. Intramuscular epinephrine only
    4. Oral activated charcoal
    Show answer

    Answer: B. 20% intravenous lipid emulsion, given as a bolus followed by a continuous infusion

    20% intravenous lipid emulsion is the recognised first-line antidote for LAST, administered as a bolus followed by a continuous infusion alongside standard resuscitation measures.

  5. Why are ester local anaesthetics more associated with allergic reactions than amides?

    1. Esters are metabolised by plasma pseudocholinesterase into para-aminobenzoic acid (PABA), a recognised allergen, and cross-sensitivity within the ester group is expected
    2. Esters have no metabolism at all and accumulate in tissue
    3. Amides are actually more allergenic than esters
    4. Ester local anaesthetics contain penicillin as an excipient
    Show answer

    Answer: A. Esters are metabolised by plasma pseudocholinesterase into para-aminobenzoic acid (PABA), a recognised allergen, and cross-sensitivity within the ester group is expected

    Ester local anaesthetics are hydrolysed by plasma pseudocholinesterase, and one metabolic product is para-aminobenzoic acid (PABA), a known allergen. A hypersensitivity reaction to one ester predicts sensitivity to others in the ester group.

  6. Which local anaesthetic is most associated with methaemoglobinaemia, and in what population is this especially relevant?

    1. Lidocaine; relevant mainly in elderly patients
    2. Benzocaine, accounting for roughly two-thirds of reported local-anaesthetic-related cases; neonates are more susceptible to methaemoglobinaemia generally
    3. Bupivacaine; relevant only in cardiac patients
    4. Ropivacaine; relevant only during labour epidurals
    Show answer

    Answer: B. Benzocaine, accounting for roughly two-thirds of reported local-anaesthetic-related cases; neonates are more susceptible to methaemoglobinaemia generally

    Benzocaine is the causative agent in roughly two-thirds of reported local-anaesthetic-related methaemoglobinaemia cases, prompting repeated FDA advisories, particularly regarding benzocaine-containing oral products. Neonates are recognised as more susceptible to methaemoglobinaemia in general.

Paracetamol and other non-opioid analgesics

Revise the Paracetamol and other non-opioid analgesics guide

  1. What is the current understanding of paracetamol's mechanism of action?

    1. It is a well-characterised peripheral COX-1 inhibitor identical in mechanism to ibuprofen
    2. It is proposed to act through selective central cyclo-oxygenase inhibition and hypothalamic effects, but the exact mechanism is not fully established
    3. It works exclusively through mu-opioid receptor agonism
    4. It blocks voltage-gated sodium channels in peripheral nerves
    Show answer

    Answer: B. It is proposed to act through selective central cyclo-oxygenase inhibition and hypothalamic effects, but the exact mechanism is not fully established

    Paracetamol's mechanism is incompletely established. The best-supported proposal involves selective inhibition of cyclo-oxygenase within the central nervous system and an effect on the hypothalamus, which is a materially different and less certain picture than the well-defined peripheral COX mechanism of NSAIDs.

  2. At therapeutic doses, how does the body handle the toxic metabolite NAPQI?

    1. NAPQI is not produced at therapeutic doses at all
    2. A small amount of NAPQI is produced via CYP2E1 and swiftly conjugated with hepatic glutathione into nontoxic compounds
    3. NAPQI is excreted unchanged by the kidney before it can cause harm
    4. NAPQI is converted back into paracetamol by the liver
    Show answer

    Answer: B. A small amount of NAPQI is produced via CYP2E1 and swiftly conjugated with hepatic glutathione into nontoxic compounds

    At therapeutic doses, only a small fraction of paracetamol is metabolised via CYP2E1 into NAPQI, which is rapidly conjugated with hepatic glutathione to form nontoxic cysteine and mercaptate compounds — this is the normal, safe pathway.

  3. What actually causes liver injury in paracetamol overdose?

    1. Paracetamol itself directly destroys hepatocytes
    2. Increased NAPQI production depletes glutathione stores, and the excess NAPQI binds hepatic macromolecules, causing centrilobular necrosis
    3. Paracetamol overdose causes an allergic hypersensitivity reaction in the liver
    4. The kidney fails first, and liver injury is a secondary consequence
    Show answer

    Answer: B. Increased NAPQI production depletes glutathione stores, and the excess NAPQI binds hepatic macromolecules, causing centrilobular necrosis

    In overdose, increased NAPQI production outpaces the liver's glutathione supply. The unconjugated NAPQI binds covalently to hepatic macromolecules, particularly mitochondrial proteins, producing centrilobular (zone 3) hepatocellular necrosis.

  4. Why is N-acetylcysteine most effective when given within 8 hours of an acute paracetamol overdose?

    1. It has no time-dependence and works equally well at any interval
    2. It works by replenishing/mimicking glutathione to prevent NAPQI from binding hepatic macromolecules, before that binding and the resulting necrosis have already occurred
    3. It only works if given before the drug is absorbed
    4. It directly reverses hepatic necrosis that has already occurred
    Show answer

    Answer: B. It works by replenishing/mimicking glutathione to prevent NAPQI from binding hepatic macromolecules, before that binding and the resulting necrosis have already occurred

    N-acetylcysteine acts by preventing NAPQI from binding to hepatic macromolecules. Once that binding has already happened and hepatocyte injury is underway, the drug's benefit diminishes, which is why early administration, ideally within 8 hours, matters so much.

  5. Why are chronic alcohol users at higher hepatotoxicity risk from the same paracetamol dose as other patients?

    1. Alcohol has no effect on paracetamol metabolism
    2. Chronic alcohol use upregulates CYP2E1, increasing NAPQI production from a given dose, and can also affect glutathione reserves
    3. Alcohol blocks paracetamol absorption entirely, so more must be taken to reach the same effect
    4. Chronic alcohol users metabolise paracetamol entirely through a nontoxic pathway
    Show answer

    Answer: B. Chronic alcohol use upregulates CYP2E1, increasing NAPQI production from a given dose, and can also affect glutathione reserves

    Chronic alcohol ingestion is a documented risk factor because it upregulates CYP2E1, the enzyme that produces NAPQI, meaning more toxic metabolite is generated from the same paracetamol dose than in a person without that enzyme induction.

  6. Why does the FDA-approved consumer label warn against taking a paracetamol-containing product together with another acetaminophen-containing product?

    1. Because the two drugs interact pharmacodynamically to increase pain
    2. Because doing so risks unknowingly exceeding the maximum daily acetaminophen dose and causing severe liver damage
    3. Because it voids the product warranty
    4. Because acetaminophen from two products cancels out and neither works
    Show answer

    Answer: B. Because doing so risks unknowingly exceeding the maximum daily acetaminophen dose and causing severe liver damage

    Multiple over-the-counter and prescription products contain acetaminophen (for example combination cold remedies and combination analgesics). Taking more than one at a time is a common, real route to accidental overdose and severe liver damage, which is exactly what the label warning is designed to prevent.

Neuromuscular blockers

Revise the Neuromuscular blockers guide

  1. What distinguishes the mechanism of a depolarising neuromuscular blocker from a nondepolarising one?

    1. Depolarising agents block the receptor without ever activating it; nondepolarising agents activate it repeatedly
    2. A depolarising agent (succinylcholine) binds the nicotinic receptor and causes sustained depolarisation and eventual refractoriness; a nondepolarising agent competitively blocks acetylcholine from binding the receptor without activating it
    3. Both classes work identically at the molecular level and differ only in duration
    4. Depolarising agents act at the presynaptic membrane; nondepolarising agents act only postsynaptically
    Show answer

    Answer: B. A depolarising agent (succinylcholine) binds the nicotinic receptor and causes sustained depolarisation and eventual refractoriness; a nondepolarising agent competitively blocks acetylcholine from binding the receptor without activating it

    Succinylcholine, the depolarising agent, binds the postsynaptic nicotinic receptor and causes sustained depolarisation, producing transient fasciculations followed by paralysis as sodium channels become refractory. Nondepolarising agents instead competitively occupy the receptor, preventing acetylcholine binding without ever activating the channel.

  2. The succinylcholine boxed warning for pediatric hyperkalaemic cardiac arrest is most closely associated with what underlying finding?

    1. An unrelated cardiac arrhythmia present from birth
    2. An undiagnosed skeletal muscle myopathy, such as Duchenne muscular dystrophy, in an apparently healthy child
    3. A known allergy to eggs
    4. Concurrent use of an ACE inhibitor
    Show answer

    Answer: B. An undiagnosed skeletal muscle myopathy, such as Duchenne muscular dystrophy, in an apparently healthy child

    Reports of ventricular dysrhythmias, cardiac arrest and death from acute rhabdomyolysis with hyperkalaemia after succinylcholine in apparently healthy paediatric patients were frequently later explained by an undiagnosed skeletal muscle myopathy such as Duchenne muscular dystrophy, whose clinical signs had not yet been recognised.

  3. Why is succinylcholine contraindicated after the acute phase of a major burn injury?

    1. It has no relevant risk in burns and the contraindication is outdated
    2. Beyond the acute phase, upregulated extrajunctional receptors can respond to succinylcholine with severe, potentially fatal hyperkalaemia
    3. Burn patients metabolise succinylcholine too slowly, prolonging paralysis only
    4. Succinylcholine causes burns to worsen directly
    Show answer

    Answer: B. Beyond the acute phase, upregulated extrajunctional receptors can respond to succinylcholine with severe, potentially fatal hyperkalaemia

    After the acute phase of major burns, multiple trauma, extensive denervation, or upper motor neuron injury, succinylcholine can cause severe hyperkalaemia through its action on upregulated extrajunctional nicotinic receptors, which can result in cardiac arrest — this is why the label specifically contraindicates it in that setting.

  4. Which reversal agent is selective for aminosteroid nondepolarising blockers such as rocuronium and vecuronium?

    1. Neostigmine
    2. Sugammadex, which physically encapsulates aminosteroid agents
    3. Naloxone
    4. Dantrolene
    Show answer

    Answer: B. Sugammadex, which physically encapsulates aminosteroid agents

    Sugammadex encapsulates aminosteroid nondepolarising agents (rocuronium, vecuronium), providing rapid, targeted reversal. It is not effective for benzylisoquinolinium agents such as atracurium, cisatracurium or mivacurium, for which neostigmine remains the relevant reversal option.

  5. Why must neostigmine always be given together with an anticholinergic such as glycopyrrolate?

    1. To speed up neostigmine's onset of action
    2. Because neostigmine inhibits acetylcholinesterase systemically, not only at the neuromuscular junction, and would otherwise cause muscarinic side effects such as bradycardia
    3. Because neostigmine alone has no effect on neuromuscular blockade
    4. To prevent malignant hyperthermia
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    Answer: B. Because neostigmine inhibits acetylcholinesterase systemically, not only at the neuromuscular junction, and would otherwise cause muscarinic side effects such as bradycardia

    Neostigmine's acetylcholinesterase inhibition is not confined to the neuromuscular junction. Left unopposed, it produces muscarinic effects such as bradycardia, so an anticholinergic is co-administered specifically to offset those effects while the nicotinic reversal at the neuromuscular junction is retained.

  6. What is the essential safety requirement for administering any neuromuscular blocking agent?

    1. The patient must be conscious and cooperative throughout
    2. Personnel and facilities for resuscitation and life support must be available, with an antagonist readily accessible, because these drugs paralyse the muscles of respiration along with every other skeletal muscle
    3. The drug must be given only by mouth to avoid overdose
    4. No monitoring is required once the drug has been given
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    Answer: B. Personnel and facilities for resuscitation and life support must be available, with an antagonist readily accessible, because these drugs paralyse the muscles of respiration along with every other skeletal muscle

    Because neuromuscular blockers paralyse the muscles of breathing along with all other skeletal muscle, administration should never occur without personnel and facilities for resuscitation and life support, and a reversal agent readily available.