What is the maximum dose of intravenous (IV) Hydralazine?

From the Guidelines

The maximum dose of intravenous hydralazine is 20 mg per dose, as recommended by the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults 1.

Key Points

• The initial dose of hydralazine is typically 10 mg via slow IV infusion, with a maximum initial dose of 20 mg 1.
• The dose can be repeated every 4-6 hours as needed, with careful monitoring of blood pressure and heart rate 1.
• Hydralazine works as a direct arterial vasodilator, relaxing vascular smooth muscle and decreasing peripheral resistance, which leads to blood pressure reduction 1.
• Caution should be exercised when administering hydralazine due to the risk of rapid blood pressure reduction, potentially causing reflex tachycardia, and the need for dose adjustments in patients with renal impairment or coronary artery disease 1.

Administration and Monitoring

• Hydralazine should be administered as a slow IV infusion, with careful monitoring of blood pressure and heart rate 1.
• The onset of action occurs within 10-30 minutes, and the fall in blood pressure lasts 2-4 hours 1.
• Continuous monitoring of blood pressure and heart rate is essential during IV administration to prevent target organ damage and ensure safe use of the medication 1.

Special Considerations

• Hydralazine is not a desirable first-line agent for acute treatment in most patients due to its unpredictability of response and prolonged duration of action 1.
• The medication should be used cautiously in patients with coronary artery disease due to the risk of myocardial ischemia from reflex tachycardia 1.
• Dose adjustments may be necessary for patients with renal impairment, and the drug should be used with caution in patients with other comorbidities 1.

From the FDA Drug Label

When there is urgent need, therapy in the hospitalized patient may be initiated intramuscularly or as a rapid intravenous bolus injection directly into the vein. The usual dose is 20 to 40 mg, repeated as necessary The maximum dose of intravenous (IV) Hydralazine is not explicitly stated in the drug label.

• The label only provides the usual dose of 20 to 40 mg, repeated as necessary. 2

From the Research

Maximum Dose of Intravenous Hydralazine

• The maximum dose of intravenous hydralazine is not explicitly stated in the provided studies, but the doses used in the studies can be reviewed:
  • In the study 3, patients received an initial dose of 5 mg of hydralazine, which was repeated when at least 20% reduction in arterial pressure was not achieved.
  • In the study 4, the mean dose of intravenous hydralazine was 11.4 ± 4.3 mg.
  • In the study 5, the maximum dose of hydralazine was not specified, but patients received 5 mg as a slow bolus dose given intravenously, and repeated every 20 min up to a maximum of five doses.
  • In the study 6, patients received a bolus injection of hydralazine, with a mean dose of 6.68 ± 1.66 mg, while the control group received a continuous drip with a mean dose of 20.07 ± 11.38 mg.

Dosage Comparison

• The studies suggest that the dose of intravenous hydralazine can vary depending on the patient's condition and the desired outcome:
  • The study 3 used a dose of 5 mg, which was repeated as needed.
  • The study 4 reported a mean dose of 11.4 ± 4.3 mg.
  • The study 5 used a dose of 5 mg, repeated every 20 min up to a maximum of five doses.
  • The study 6 compared bolus injection and continuous drip, with the bolus injection requiring a lower mean dose of 6.68 ± 1.66 mg.

Safety and Efficacy

• The studies also report on the safety and efficacy of intravenous hydralazine:
  • The study 3 reported that intravenous hydralazine was an alternative when rapid arterial pressure reduction was needed, but side effects were observed in 25% of patients.
  • The study 4 reported that intravenous hydralazine was commonly prescribed for non-urgent cases of hypertension, but changes in systolic blood pressure were highly variable and associated with hypotension.
  • The study 5 reported that intravenous hydralazine was effective in lowering blood pressure, but palpitations and maternal tachycardia occurred more frequently in patients treated with hydralazine.
  • The study 6 reported that hydralazine bolus injection was equally safe and more effective than continuous drip in the management of hypertensive emergencies in pregnancy.