Maximum Daily Dose of Hydralazine
The maximum recommended daily dose of hydralazine for adults is 300 mg in divided doses. 1
Dosing Guidelines for Adults
- Initial dosing: 25-50 mg 3-4 times daily 1
- Titration: Gradual increase as needed for blood pressure control
- Maximum daily dose: 300 mg in divided doses 1
- Safety threshold: Doses above 150 mg daily increase the risk of drug-induced systemic lupus erythematosus 1
Special Considerations
Heart Failure Combination Therapy
- When used in combination with isosorbide dinitrate for heart failure:
- Target dose: 75 mg hydralazine/40 mg isosorbide dinitrate three times daily
- Maximum daily dose in this combination: 225 mg hydralazine 1
Acetylator Status Impact
- Slow acetylators achieve therapeutic effect at lower doses
- Fast acetylators may require higher doses within the maximum limit 1
- The dose that elicits 50% of maximum response (D50) is 0.87 mg/kg for slow acetylators and 1.68 mg/kg for fast acetylators 2
Dosing Frequency
- Despite the drug's relatively short half-life, evidence suggests twice-daily dosing may be sufficient when using conventional formulations 3
- For patients with renal impairment (creatinine clearance <35 ml/min), the duration of action is significantly longer (14.3 ± 1.4 hours vs 7.9 ± 0.5 hours) 4
Monitoring Requirements
- Regular monitoring is required with prolonged therapy:
- Monitor for signs of drug-induced lupus erythematosus, especially at doses >150 mg/day
- Monitor for peripheral neuritis (paresthesia, numbness, tingling) 5
Pediatric Dosing
- Initial dose: 0.75 mg/kg of body weight daily in four divided doses
- Maximum dose: 7.5 mg/kg/day up to 200 mg/day 1, 5
Important Precautions
- Use with caution in patients with:
- Suspected coronary artery disease (risk of anginal attacks and myocardial ischemia)
- Mitral valvular disease (may increase pulmonary artery pressure)
- Cerebrovascular disease
- Advanced renal damage 5
- Avoid abrupt discontinuation as this may lead to rebound hypertension
- Consider adding pyridoxine if peripheral neuritis develops 5
Hydralazine's vasodilatory effects can be optimized while minimizing adverse effects by carefully titrating the dose and maintaining appropriate monitoring, particularly when approaching or exceeding the 150 mg daily threshold.