What are the typical doses of hydralazine (antihypertensive medication) that can be ordered?

Hydralazine Dosing Guidelines

Hydralazine can be ordered at initial doses of 10-25 mg three to four times daily, with gradual titration up to a maximum of 300 mg daily in divided doses for hypertension management. 1

Dosing Regimens by Indication

For Hypertension:

• 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 and beyond: Increase to 50 mg four times daily 1
• Maximum dose: Up to 300 mg daily in resistant cases 1
• Maintenance: Adjust to lowest effective dose 1

For Heart Failure (with Isosorbide Dinitrate):

• Fixed-dose combination:

  • Initial: 20 mg isosorbide dinitrate/37.5 mg hydralazine three times daily 2
  • Target: 40 mg isosorbide dinitrate/75 mg hydralazine three times daily 2
  • Mean dose achieved in clinical trials: ~175 mg hydralazine daily 2

• Separate administration:

  • Initial: 25-50 mg hydralazine three to four times daily 2
  • Target: Up to 300 mg hydralazine daily in divided doses 2

Dosing Frequency Considerations

Research suggests that hydralazine can be effectively administered twice daily despite its relatively short half-life:

• Studies have shown no significant difference in blood pressure control between twice-daily and four-times-daily dosing regimens 3, 4
• Slow-release formulations can be given twice daily with similar efficacy to conventional formulations given more frequently 5, 4

Special Population Considerations

Pediatric Dosing:

• Starting dose: 0.75 mg/kg daily in four divided doses 1
• Maximum dose: 7.5 mg/kg daily or 200 mg daily 1
• Gradual titration over 3-4 weeks 1

Resistant Hypertension:

• Consider lower doses of hydralazine combined with a thiazide, reserpine, or beta-blocker 1
• Individual titration is essential to ensure the lowest possible therapeutic dose of each drug 1

Monitoring and Safety Considerations

• Monitor for hypotension (occurs in approximately 11% of patients) 6
• Watch for reflex tachycardia, especially when not combined with beta-blockers 6, 7
• At higher doses, there is increased risk of drug-induced lupus-like syndrome 6
• The incidence of toxic reactions is higher in patients receiving large doses 1

Clinical Pearls

• Hydralazine has a rapid onset of action (10 minutes) but relatively short duration (2-4 hours), though effects may last up to 12 hours 6
• Administration with food results in higher plasma levels 1
• When combined with beta-blockers (like propranolol), hydralazine provides more effective blood pressure control with fewer side effects than either agent alone 7
• In heart failure, hydralazine combined with isosorbide dinitrate has shown a 43% relative risk reduction in mortality 2

Remember that while lower doses may provide some benefit, clinical trials showing mortality benefit in heart failure achieved mean doses of approximately 175 mg hydralazine daily 2. Therefore, targeting these evidence-based doses when tolerated is recommended for optimal outcomes.