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Usual Dosing (Adults)

When there is urgent need, therapy in the hospitalized patient may be initiated intramuscularly or as a rapid intravenous bolus injection directly into the vein. Hydralazine Hydrochloride Injection should be used only when the drug cannot be given orally. The usual dose is 20 to 40 mg, repeated as necessary.

Certain patients (especially those with marked renal damage) may require a lower dose. Blood pressure should be checked frequently. It may begin to fall within a few minutes after injection, with the average maximal decrease occurring in 10 to 80 minutes. In cases where there has been increased intracranial pressure, lowering the blood pressure may increase cerebral ischemia. Most patients can be transferred to oral hydralazine hydrochloride within 24 to 48 hours.

The product should be used immediately after the vial is opened. The product should not be added to infusion solutions. Hydralazine Hydrochloride Injection may discolor upon contact with metal; discolored solutions should be discarded.

Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.

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.

HTN: Initially 10 mg qid - increase by 10-25 mg/dose q 2-5 days (maximum: 300 mg/day). Acute hypertension: Initially 10-20 mg IM/IV q 4-6 hours prn. May increase to 40 mg/dose (change to oral therapy as soon as possible).

CHF: Initially 10 to 25mg orally 3-4 times/day. Maintenance: Typically 200 to 600 mg daily in 2-4 divided doses. 

Renal Dosing

dialysis [>50 ml/min]: No changes
[10-50]: Give usual dose q8h or less.  
[<10 ]: Give q8-16 hours in fast acetylators and q12-24 hours in slow acetylators.


dialysis Give q8 to 16 hours in fast acetylators and q 12-24 hours in slow acetylators.


National Institutes of Health, U.S. National Library of Medicine, DailyMed Database.
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