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Hydralazine Dosage

Applies to the following strength(s): 25 mg ; 50 mg ; 10 mg ; 100 mg ; 20 mg/mL

The information at is not a substitute for medical advice. Always consult your doctor or pharmacist.

Usual Adult Dose for:

Additional dosage information:

Usual Adult Dose for Hypertension

Initial dose: 10 mg orally 4 times a day for the first 2 to 4 days. Increase to 25 mg orally 4 times a day for the balance of the first week.
For the second and subsequent weeks, increase dosage to 50 mg orally 4 times a day.
Maintenance dose: Adjust dosage to the lowest effective levels.

Usual Adult Dose for Hypertensive Emergency

Usual dose: 20 to 40 mg IV or IM, repeated as necessary. Certain patients (especially those with marked renal damage) may require a lower dose.

Usual Adult Dose for Congestive Heart Failure

Initial dose: 10 mg orally 4 times a day
Maintenance dose: Doses up to 800 mg three times daily have been effective in reducing afterload in the treatment of congestive heart failure

Renal Dose Adjustments

CrCl < 10 mL/min: The dosing interval should be increased to every 8 to 16 hours in fast acetylators and every 12 to 24 hours in slow acetylators.

CrCl 10-50 mL/min: The dosing interval should be increased to every 8 hours.

Liver Dose Adjustments

Because hydralazine is primarily metabolized by the liver, it is recommended that dose increments be made cautiously (frequent blood pressure checks and monitoring for side effects) in patients with liver disease.

Dose Adjustments

In a few resistant patients, up to 300 mg of hydralazine daily may be required for a significant antihypertensive effect. In such cases, a lower dosage of hydralazine combined with a thiazide and/or reserpine or a beta blocker may be considered. However, when combining therapy, individual titration is essential to ensure the lowest possible therapeutic dose of each drug.


Up to 20% of patients who receive 400 mg/day or more develop a systemic lupus erythematosus syndrome. Some experts recommended checking the acetylator status of the patient before giving higher doses. Fast acetylators can handle dosage increases more safely. Close monitoring for signs and symptoms of hydralazine-induced lupus has been strongly recommended.


No supplemental dose is necessary with hemo- or peritoneal dialysis.

Other Comments

Blood pressure of patients receiving IV or IM hydralazine may fall a few minutes after injection, with the average maximum decrease occurring in 10 to 80 minutes. Most patients can be transferred to oral hydralazine within 24 to 48 hours.