Maximum Dose of Hydralazine
The maximum daily dose of hydralazine is 300 mg in divided doses for adults, and 7.5 mg/kg/day up to 200 mg/day for children. 1, 2
Adult Dosing Guidelines
Standard Dosing
- Initial dose: 10 mg four times daily for the first 2-4 days 1
- First week: Increase to 25 mg four times daily 1
- Second week onward: Increase to 50 mg four times daily 1
- Maximum daily dose: 300 mg in divided doses 1, 3
Dosing in Resistant Hypertension
- Initial dose: 25 mg three times daily 2
- Titrate upward as needed 2
- Maximum dose: 150 mg daily to avoid drug-induced systemic lupus erythematosus 2
Pediatric Dosing
- Initial dose: 0.75 mg/kg/day in four divided doses 1
- Titration: Gradually increase over 3-4 weeks 1
- Maximum dose: 7.5 mg/kg/day up to 200 mg/day 2
Administration Considerations
Dosing Frequency
- Standard administration: Four times daily 1
- When combined with beta-blockers: Three times daily may be sufficient 4
Factors Affecting Dosing
- Acetylator status: Slow acetylators achieve therapeutic effect at lower doses while fast acetylators may require higher doses 3, 5
- Renal function: Duration of action is longer in patients with impaired renal function (CCr <35 ml/min) 6
Special Considerations
Heart Failure
- When used in combination with isosorbide dinitrate for heart failure:
Safety Concerns
- Doses above 150 mg daily increase risk of drug-induced systemic lupus erythematosus 2
- Regular monitoring is required with prolonged therapy:
- Complete blood counts
- Antinuclear antibody titers 1
Clinical Pearls
- For resistant hypertension, hydralazine should be used with appropriate background diuretic and beta-blocker therapy to counteract increased sympathetic tone and sodium retention 2
- In heart failure patients, hydralazine combined with nitrates has shown significant mortality benefits 3
- The unpredictability of response makes hydralazine less desirable as a first-line agent for acute hypertension treatment 3
Remember that while the FDA-approved maximum dose is 300 mg daily for adults, the American Heart Association recommends limiting to 150 mg daily in resistant hypertension to minimize the risk of drug-induced lupus syndrome.