Hydralazine Hydrochloride
Pronunciation: (hye-DRAL-a-zeen).
- Generic name
- hydralazine hydrochloride
- Brand names
- Hydralazine Accord, Hydralazine GH, Hydralazine Sandoz, Apresoline, Hypres, Apresol
- Drug class
- Antihypertensive; Vasodilator
Availability and supply rules vary by country
Trade names by country: Canada
Australia: · Full directory
What hydralazine hydrochloride is and how it works
Uses, formulations, monitoring, and supply rules can differ by patient, product, and country. Follow the exact local product information and professional advice.
Mechanism of action: how hydralazine hydrochloride works
Hydralazine is a direct-acting vasodilator that primarily relaxes arteriolar smooth muscle. This leads to decreased peripheral vascular resistance and a reduction in blood pressure. The exact mechanism is not fully understood, but it is believed to involve interference with calcium ion movement in vascular smooth muscle. (1) (2)
What hydralazine hydrochloride is used for
Hypertension
Hypertension (2)
Hypertensive crisis
Hypertensive crisis (2)
Preeclampsia/Eclampsia (in combination with other agents)
Preeclampsia/Eclampsia (in combination with other agents) (2)
Heart failure (as an adjunct in specific cases)
Heart failure (as an adjunct in specific cases) (2)
Before taking hydralazine hydrochloride
Do not take / not appropriate for
- hypersensitivity to hydralazine, idiopathic systemic lupus erythematosus, and severe tachycardia with heart failure due to high-output states. (Contraindication) (2)
Tell your clinician about
(2)How to take hydralazine hydrochloride
- General Instructions: Take hydralazine exactly as prescribed by your doctor. Do not take more or less than directed.. Adult Dosing: For hypertension: initial dose is typically 10 mg orally 4 times daily for the first 2-4 days, then gradually increased by your prescriber; the FDA label describes a titration up to 25 mg 4 times daily, then 50 mg 4 times daily, with a maximum of up to 300 mg/day used in some resistant cases. Your prescriber will set your specific target dose. For heart failure: dosing is individualized and often combined with isosorbide dinitrate.. Pediatric Dosing: Dosing in children is based on weight and must be determined by a pediatric specialist.. Administration: Take with or without food, but try to be consistent, since food can increase hydralazine levels in the blood. Swallow tablets whole with water. For injections, administration is by a healthcare professional.. When To Stop: Do not stop taking hydralazine suddenly unless instructed by your doctor, as this may cause a dangerous increase in blood pressure.. Storage: Store at 20-25°C (68-77°F) [controlled room temperature], away from moisture, heat, and light, in a tight, light-resistant container. Keep out of reach of children.
- This page does not provide a dose calculator. Dosing must follow the prescriber, pharmacist, or product label.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (2)
Missed dose
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose. Do not take two doses at the same time.
Overdose
Symptoms of overdose may include severe dizziness, fainting, rapid heartbeat, or shock. Seek emergency medical attention or call your local poison control center immediately. (2)
Side effects
Side effects and their urgency vary; report severe, persistent, or concerning symptoms to a healthcare professional.
Headache
Incidence: Reported in the clinician-authored database; frequency not established
Nausea
Incidence: Reported in the clinician-authored database; frequency not established
Vomiting
Incidence: Reported in the clinician-authored database; frequency not established
Diarrhea
Incidence: Reported in the clinician-authored database; frequency not established
Tachycardia
Incidence: Reported in the clinician-authored database; frequency not established
Palpitations
Incidence: Reported in the clinician-authored database; frequency not established
Anorexia
Incidence: Reported in the clinician-authored database; frequency not established
Lupus-like syndrome
Incidence: Reported in the clinician-authored database; frequency not established
Signs of lupus-like syndrome (joint pain, rash, unexplained fever)
(2)Numbness, tingling, or pins-and-needles sensations (possible peripheral neuritis)
(2)Chest pain or symptoms suggesting reduced blood flow to the heart
(2)Signs of an allergic reaction, severe dizziness, or fainting
(1)Serious warnings
May cause a lupus-like syndrome with prolonged use (monitor for joint pain, rash, or unexplained fever — serious
Symptoms: May cause a lupus-like syndrome with prolonged use (monitor for joint pain, rash, or unexplained fever; your clinician may check ANA and kidney function). May cause peripheral neuritis (numbness, tingling, or pins-and-needles sensations) — your clinician may recommend a vitamin B6 (pyridoxine) supplement if this develops. Can trigger anginal (chest pain) attacks or signs of reduced blood flow to the heart, especially in people with underlying coronary artery disease. Use with caution in patients with kidney or liver impairment. Monitor for signs of hypotension and tachycardia. May cause fluid retention; monitor for swelling or weight gain. Not recommended during pregnancy unless clearly needed (FDA Pregnancy Category C).
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2)
Contraindications, corrected against the FDA label — serious
Symptoms: Contraindications, corrected against the FDA label: hypersensitivity to hydralazine, idiopathic systemic lupus erythematosus, coronary artery disease, mitral valvular rheumatic heart disease, and severe tachycardia with heart failure due to high-output states. (The FDA label lists coronary artery disease and mitral valvular rheumatic heart disease as contraindications, not merely cautions.) Use with caution in patients with cerebrovascular disease, renal or hepatic impairment, and in the elderly.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2)
Interactions
| Medicine or test | Effect | Action |
|---|---|---|
| Recorded interactions | Hydralazine may interact with other antihypertensive agents, beta-blockers, diuretics, and monoamine oxidase inhibitors (MAOIs). It can enhance the hypotensive effects of other drugs and may increase the risk of side effects. Always inform your healthcare provider about all medicines and supplements you are taking. | (1) |
| Diazoxide | Combining hydralazine with diazoxide may cause profound, excessive drops in blood pressure. Use only under close medical supervision if both are prescribed. | (2) |
| Food | Food increases hydralazine blood levels. Try to take doses consistently in relation to meals, as your prescriber directs. | (2) |
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy
FDA Pregnancy Category C: animal studies showed teratogenic effects at high doses, and there are no adequate, well-controlled studies in pregnant women. Hydralazine is not recommended during pregnancy unless the potential benefit justifies the potential risk to the fetus; it is sometimes used for severe hypertension in pregnancy under close medical supervision. (2)
Breastfeeding
Breastfeeding-specific safety data are not established in the sources reviewed for this medicine. Discuss breastfeeding with your healthcare provider before use. (2)
Children
Frequency: Not applicable.. Weight Based: Not recommended for pediatric use.. Max Daily Dose: Not applicable.. Max Single Dose: Not applicable.. Age Restrictions: Safety not established in children. (2)
Renal_impairment
Use with caution in patients with renal or hepatic impairment; the FDA label does not specify a numeric renal dose adjustment for hydralazine tablets. Your prescriber will individualize dosing and monitoring. (2)
Hepatic_impairment
Use with caution in patients with renal or hepatic impairment; the FDA label does not specify a numeric renal dose adjustment for hydralazine tablets. Your prescriber will individualize dosing and monitoring. (2)
Monitoring
(2)Storage
Store at 20-25°C (68-77°F) [controlled room temperature], away from moisture, heat, and light, in a tight, light-resistant container. Keep out of reach of children.
Professional information
Clinician-facing context only. This section does not replace current product labeling.
General
Indication: Hypertension
Dose summary: Hypertension: 10 mg 4 times daily for 2-4 days, then 25 mg 4 times daily for the remainder of week 1, then 50 mg 4 times daily for subsequent weeks as needed; up to 300 mg/day total may be required in resistant hypertension (per FDA label), though combination therapy is often preferred over high-dose monotherapy.
Renal context: The FDA label does not specify a numeric renal dose adjustment; use with caution and individualize dosing in renal impairment. (1) (2)
Frequently asked questions
What is hydralazine used for?
Hydralazine is used to treat high blood pressure (hypertension) and heart failure. It helps relax blood vessels, making it easier for the heart to pump blood.
How quickly does hydralazine work?
Hydralazine typically starts to lower blood pressure within 20–30 minutes after oral administration, with peak effects in 1–2 hours.
Can I stop taking hydralazine if I feel better?
No, do not stop taking hydralazine without consulting your doctor. Stopping suddenly can cause your blood pressure to rise rapidly.
What should I do if I experience side effects?
Mild side effects may improve over time. If you experience serious symptoms such as chest pain, severe dizziness, or signs of an allergic reaction, seek medical attention immediately.
Is hydralazine safe during pregnancy?
Hydralazine may be used during pregnancy if clearly needed, especially for severe hypertension, but only under close medical supervision.
Can hydralazine be used with other blood pressure medicines?
Yes, hydralazine is often used in combination with other antihypertensive agents. Your doctor will determine the best combination for you.
How is hydralazine different from other blood pressure medications?
Hydralazine is a direct vasodilator, meaning it directly relaxes blood vessel walls. It is often used when other medications are not effective or suitable.
What happens if I take too much Hydralazine?
Taking too much Hydralazine can lead to symptoms such as severe hypotension (low blood pressure), rapid heartbeat, headache, and dizziness. In extreme cases, it may cause shock or coma. If you suspect an overdose, seek immediate emergency medical attention. Do not attempt to self-treat, as prompt professional intervention is crucial for managing potential complications.
Can I drink alcohol while taking Hydralazine?
It is generally advisable to limit or avoid alcohol consumption while taking Hydralazine. Alcohol can exacerbate the blood pressure-lowering effects of vasodilators, potentially leading to excessive dizziness, lightheadedness, and fainting. This increased risk of hypotension can be dangerous, especially when standing up. Always consult your healthcare provider regarding alcohol intake with your medication.
What is the mechanism of action of hydralazine hydrochloride?
Hydralazine is a direct-acting vasodilator that primarily relaxes arteriolar smooth muscle. This leads to decreased peripheral vascular resistance and a reduction in blood pressure. The exact mechanism is not fully understood, but it is believed to involve interference with calcium ion movement in vascular smooth muscle. (1) (2)
What is the generic name of Hydralazine Hydrochloride?
The generic name is hydralazine hydrochloride. It is sold under brand names including Hydralazine Accord, Hydralazine GH, Hydralazine Sandoz, Apresoline, Hypres, Apresol.
What class of drug is hydralazine hydrochloride?
Hydralazine Hydrochloride is classed as: Antihypertensive; Vasodilator.
References
- MedGuideGlobal clinician-authored medicine record: hydralazineMedGuideGlobal · null · accessed 2026-08-06 · source 1
- Hydralazine Hydrochloride Tablets, USP — prescribing informationU.S. Food and Drug Administration · United States · accessed 2026-08-06 · source 2
- HYDRALAZINE HYDROCHLORIDE TABLET [COUPLER LLC] — US prescribing information (DailyMed SPL)U.S. National Library of Medicine (DailyMed) · US · accessed 2026-08-14 · source 3
- Hydralazine — patient drug information (MedlinePlus)U.S. National Library of Medicine (MedlinePlus) · US · accessed 2026-08-14 · source 4
- Hydralazine Hydrochloride — FDA approval record (Drugs@FDA ANDA040858)U.S. Food and Drug Administration · US · accessed 2026-08-14 · source 5
- hydralazine — RxNorm normalized drug concept (RXCUI 5470)U.S. National Library of Medicine (RxNorm) · US · accessed 2026-08-14 · source 6
Brand names by country
Single-ingredient hydralazine hydrochloride names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
Canada
- APRESOLINE