Is a 5mg formulation of hydralazine (direct vasodilator) available?

Hydralazine 5mg Formulation Availability

No, a 5mg formulation of hydralazine is not available in standard clinical practice. The lowest recommended starting doses are substantially higher than 5mg across all clinical indications.

Available Formulations and Dosing

Intravenous Formulation

• The initial IV dose for hypertensive emergencies is 10-20 mg as a slow bolus, repeated every 4-6 hours as needed 1, 2, 3
• No 5mg IV formulation exists in standard practice 2, 3

Oral Formulations

• Conventional tablets: The lowest starting dose is 25-50 mg administered three to four times daily 1, 4
• Fixed-dose combination (with isosorbide dinitrate): Starts at 37.5 mg hydralazine/20 mg isosorbide dinitrate three times daily 1
• Slow-release formulation: Studied at doses of 200 mg once daily, not available in 5mg strength 5, 6

Clinical Context for Dosing

Heart Failure with Reduced Ejection Fraction

• Initial dosing begins at 25-50 mg three to four times daily, always combined with isosorbide dinitrate 1, 4
• Target dose is 75 mg hydralazine three times daily (225 mg total daily) 1
• Mean dose achieved in clinical trials was approximately 175 mg total daily 1
• Maximum daily dose is 300 mg in divided doses 1, 4

Hypertension Management

• Oral dosing for blood pressure control starts at 25-50 mg three to four times daily 4, 7
• Studies demonstrate no need to administer hydralazine more than twice daily when combined with beta-blockers and diuretics 5, 8, 6

Important Clinical Considerations

A 5mg dose would be subtherapeutic for all approved indications. The pharmacokinetic profile and dose-response relationship of hydralazine require substantially higher doses to achieve clinical benefit 7, 8:

• The daily dose that elicits 50% of maximum antihypertensive response (D50) is 0.87 mg/kg for slow acetylators and 1.68 mg/kg for fast acetylators 7
• For a 70kg patient, this translates to approximately 60-120 mg daily minimum for half-maximal effect 7
• Maximum antihypertensive response (Emax) is 9.4 mm Hg, achieved with doses well above 5mg 7

Common Pitfall to Avoid

• Never attempt to use hydralazine at doses below 10mg IV or 25mg oral, as these doses fall far below the therapeutic threshold established in clinical trials and pharmacokinetic studies 1, 7