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Below are the general guidelines for doing Hydralazine. Note that these dosages may be adjusted on a case-by-case basis for individual patients. Always follow your prescribing physician’s instructions for taking Hydralazine.

The following information comes from DailyMed, an FDA label information provider.

What if I miss a dose of Hydralazine?

According to Mayo Clinic, if you miss a dose of Hydralazine, take the missed dose immediately unless you are closer to the time of your next dose. Never double doses.

What if I overdose on Hydralazine?

Acute Toxicity

No deaths due to acute poisoning have been reported. Highest known dose survived: adults, 10 g orally.

Oral LD50 in rats: 173 and 187 mg/kg.

Note: This does not mean you should ever double doses or take more than prescribed. Taking too much can cause low blood pressure additionally.

Signs and Symptoms

Signs and symptoms of overdosage include hypotension, tachycardia, headache, and generalized skin flushing.

Complications can include myocardial ischemia and subsequent myocardial infarction, cardiac arrhythmia, and profound shock.


There is no specific antidote.

The gastric contents should be evacuated, taking adequate precautions against aspiration and for protection of the airway. An activated charcoal slurry may be instilled if conditions permit. These manipulations may have to be omitted or carried out after cardiovascular status has been stabilized, since they might precipitate cardiac arrhythmias or increase the depth of shock.

Support of the cardiovascular system is of primary importance. Shock should be treated with plasma expanders. If possible, vasopressors should not be given, but if a vasopressor is required, care should be taken not to precipitate or aggravate cardiac arrhythmia.

Tachycardia responds to beta blockers. Digitalization may be necessary, and renal function should be monitored and supported as required.

No experience has been reported with extracorporeal or peritoneal dialysis.

Dosage and Administration

Note: Typically hydralazine is not a first line medication for high blood pressure. Also, there may be instances such as emergency high blood pressure that could warrant additional doses.

Initiate therapy in gradually increasing dosages; adjust according to individual response. Start with 10 mg four times daily for the first 2 to 4 days, increase to 25 mg four times daily for the balance of the first week. For the second and subsequent weeks, increase dosage to 50 mg four times daily. For maintenance, adjust dosage to the lowest effective levels.

The incidence of toxic reactions, particularly the L.E. cell syndrome, is high in the group of patients receiving large doses of Hydralazine.

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.

How is Hydralazine supplied?

Hydralazine Hydrochloride Tablets, USP:

10 mg – Orange, round, unscored tablets debossed with ‘H’ on one side and ‘38’ on the other side in bottles of 100 (NDC code: 65977-219-10), 500 (NDC code: 65977-219-50, and 1000 (NDC code: 65977-219-01).

25 mg – Orange, round, unscored tablets debossed with ‘H’ on one side and ‘39’ on the other side in bottles of 100 (NDC code: 65977-220-10), 500 (NDC code: 65977-220-50, and 1000 (NDC code: 65977-220-01).

50 mg – Orange, round, unscored tablets debossed with ‘H’ on one side and ‘40’ on the other side in bottles of 100 (NDC code: 65977-221-10), 500 (NDC code: 65977-221-50, and 1000 (NDC code: 65977-221-01).

100 mg – Orange, round, unscored tablets debossed with ‘H’ on one side and ‘41’ on the other side in bottles of 100 (NDC code: 65977-222-10) and 500 (NDC code: 65977-222-50).

Dispense in a tight, light-resistant container as defined in the USP.

Store at 20°-25°C (68°-77°F) [See USP Controlled Room Temperature].

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.

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