What is the recommended dosage and treatment protocol for Hydralazine (Hydralazine) in managing hypertension?

Hydralazine Dosing Protocol for Hypertension Management

For hypertension management, hydralazine should be initiated at 10 mg four times daily for the first 2-4 days, then increased to 25 mg four times daily for the remainder of the first week, followed by 50 mg four times daily for maintenance therapy, with dosage adjustments based on individual response. 1

Initial Dosing and Titration

• Start with 10 mg four times daily for the first 2-4 days 1
• Increase to 25 mg four times daily for the remainder of the first week 1
• For the second and subsequent weeks, increase dosage to 50 mg four times daily 1
• Adjust maintenance dosage to the lowest effective level 1
• For resistant hypertension, doses up to 300 mg daily may be required, though this increases risk of adverse effects 1

Combination Therapy Considerations

• When blood pressure control is inadequate with hydralazine alone, consider combining with:

  • A thiazide diuretic 1
  • A beta-blocker (to counteract reflex tachycardia) 1, 2
  • Reserpine 1

• The combination of propranolol and hydralazine has been shown to be more effective than either component alone in controlling both systolic and diastolic blood pressure 2

Dosing Based on Patient Characteristics

• Acetylator status affects dose requirements:

  • Slow acetylators require lower doses (D50 of 0.87 mg/kg) 3
  • Fast acetylators require higher doses (D50 of 1.68 mg/kg) 3

• For pediatric patients (though safety and effectiveness not established in controlled trials):

  • Starting dose: 0.75 mg/kg daily in four divided doses 1
  • Gradually increase over 3-4 weeks to maximum of 7.5 mg/kg or 200 mg daily 1

Alternative Dosing Formulations

• Extended-release formulations may allow for less frequent dosing:
  • Slow-release hydralazine 200 mg once daily provides satisfactory 24-hour control in both rapid and slow acetylators 4
  • Conventional hydralazine given once daily is less effective as its hypotensive effect wanes at 24 hours 4

Monitoring and Safety Considerations

• Monitor for potential adverse effects, particularly with higher doses:

  • Blood dyscrasias (reduction in hemoglobin, leukopenia, agranulocytosis) 1
  • Lupus-like syndrome (more common with higher doses) 1
  • Reflex tachycardia (mitigated by concomitant beta-blocker therapy) 2

• Use caution when combining with:

  • MAO inhibitors 1
  • Other potent antihypertensives, especially diazoxide (risk of profound hypotension) 1

• Hydralazine should be administered with food as this results in higher plasma levels 1

Special Populations

• In pregnancy (Category C):

  • Use only if expected benefit justifies potential risk to fetus 1
  • Has been widely used in treatment of hypertension in eclampsia and preeclampsia 5

• In nursing mothers:

  • Hydralazine is excreted in breast milk 1

Clinical Pearls

• For hypertensive urgencies (diastolic >120 mmHg without acute target organ damage), oral hydralazine can be effective 5
• For hypertensive emergencies with acute target organ damage, parenteral administration is preferred 5
• Individual titration is essential to ensure the lowest possible therapeutic dose 1
• The maximum antihypertensive response (Emax) to hydralazine is approximately 9.4 mmHg reduction in diastolic blood pressure 3