What is the recommended dose and administration of hydralazine (Hydralazine) intravenous (IV) for acute management of severe hypertension or heart failure?

Hydralazine IV Dosing and Administration

For acute severe hypertension, IV hydralazine should be dosed at 20-40 mg as a rapid IV bolus, repeated as necessary, though it is NOT recommended as a first-line agent due to unpredictable response and prolonged duration of action (2-4 hours). 1, 2

FDA-Approved Dosing

• Standard dose: 20-40 mg IV bolus administered directly into the vein, repeated as necessary 1
• Onset of action: Blood pressure begins to fall within minutes, with maximal decrease occurring in 10-80 minutes 1
• Duration: Effects last 2-4 hours, with longer duration (14.3 hours) in patients with creatinine clearance <35 mL/min versus 7.9 hours in those with normal renal function 3
• Lower doses required in patients with marked renal damage 1
• Use immediately after opening vial; do not add to infusion solutions 1

Special Population: Obstetrical Patients

For preeclampsia/eclampsia, use a more conservative regimen: 5-10 mg IV bolus initially, then 5-10 mg every 20-30 minutes as needed (maximum 25 mg per cycle). 2

• This is the ONLY hypertensive emergency where hydralazine is specifically recommended as first-line therapy 2
• Treatment should be initiated within 60 minutes of severe hypertension onset 2

Why Hydralazine Is NOT First-Line for Most Hypertensive Emergencies

Hydralazine has significant limitations that make it undesirable for acute BP management in non-obstetrical patients: 2, 4

• Unpredictable blood pressure response with high variability in individual patient responses 2, 5
• Prolonged duration of action (2-4 hours) makes titration difficult 2, 4
• Reflex tachycardia can provoke myocardial ischemia, particularly in patients with coronary artery disease 2, 6
• Risk of hypotension: 11 of 94 patients (12%) experienced hypotension in one retrospective study 5

Preferred Alternative Agents for Non-Obstetrical Hypertensive Emergencies

For most hypertensive emergencies, use these agents instead: 2

• Nicardipine: 5-15 mg/h IV infusion (preferred for most situations except acute heart failure)
• Labetalol: 20-80 mg IV bolus every 10 minutes (avoid in bradycardia, acute heart failure)
• Clevidipine: 1-2 mg/h IV infusion with careful titration
• Nitroprusside: 0.25-10 μg/kg/min IV infusion (for specific emergencies)

Critical Monitoring and Safety Considerations

Check blood pressure frequently after administration as response is unpredictable 1, 2

• Hold the dose if diastolic BP <60 mmHg to prevent excessive hypotension 4
• Do NOT administer for asymptomatic hypertension with SBP <180 mmHg and DBP <110 mmHg 4, 7
• Monitor for reflex tachycardia and myocardial ischemia, especially in patients with coronary disease 2, 6
• Avoid in patients with increased intracranial pressure as lowering BP may increase cerebral ischemia 1

Common Adverse Effects

• Reflex tachycardia 2
• Headache 2
• Flushing 2
• Vomiting 2
• Hypotension (occurs in ~12% of patients) 5

Role in Chronic Heart Failure

For chronic heart failure with reduced ejection fraction, oral hydralazine (25 mg three times daily, titrated upward) combined with isosorbide dinitrate is recommended ONLY: 8

• As Step 5 therapy in resistant hypertension after optimizing other agents 8
• In Black patients with HFrEF as add-on to ACE inhibitor/beta-blocker (proven mortality benefit) 8
• In patients intolerant to ACE inhibitors (though compliance is poor due to high pill burden and side effects) 8

IV hydralazine is NOT routinely used for acute heart failure management due to risk of provoking myocardial ischemia by preserving elevated left ventricular preload 6

Key Clinical Pitfall to Avoid

The most common misuse is administering PRN hydralazine for asymptomatic BP elevations that don't meet criteria for hypertensive emergency (36% of doses given for BP <180/110 mmHg in one study). 7 Instead, optimize scheduled oral antihypertensive regimens rather than relying on PRN dosing. 7