Initial Oral Hydralazine Dose
The initial oral hydralazine dose is 25-50 mg, administered three to four times daily. 1
Standard Dosing Regimen
Start with 25-50 mg orally three to four times daily as the initial dose for heart failure with reduced ejection fraction (HFrEF), according to ACC/AHA guidelines 1
The fixed-dose combination formulation (hydralazine/isosorbide dinitrate) begins at 37.5 mg hydralazine/20 mg isosorbide dinitrate three times daily, which can be titrated to a maximum of 75 mg hydralazine/40 mg isosorbide dinitrate three times daily 1
Titration and Maximum Dosing
Maximum daily dose is 300 mg in divided doses (typically 100 mg three times daily or 75 mg four times daily) 1
The mean dose achieved in clinical trials was approximately 175 mg total daily dose (roughly 58 mg three times daily) 1
Titrate gradually over 3-4 weeks based on blood pressure response and tolerability 2
Clinical Context and Timing
Oral hydralazine onset is delayed compared to IV administration (10-30 minutes for IV vs longer for oral), with effects lasting 2-4 hours for IV formulation 3, 4
For acute management when IV is not feasible, 25-50 mg oral may be repeated every 4-6 hours as needed, not exceeding 300 mg total daily 3
Blood pressure should be reduced by no more than 25% within the first hour in hypertensive emergencies 4
Important Caveats
Always combine hydralazine with isosorbide dinitrate in HFrEF for mortality benefit (7% relative risk reduction in mortality, NNT=43) 1
Hydralazine is less predictable and less desirable as first-line therapy for acute hypertension due to variable response and prolonged duration of action 3
Monitor for reflex tachycardia, hypotension, and drug-induced lupus syndrome with chronic use 2
Food increases plasma levels, so consider consistent administration timing relative to meals 2
Pediatric Dosing Exception
- In pediatric patients, start at 0.75 mg/kg daily in four divided doses, titrating over 3-4 weeks to a maximum of 7.5 mg/kg or 200 mg daily, whichever is less 2