What is the recommended dosing for intravenous (IV) hydralazine for managing severe hypertension?

From the Guidelines

For managing severe hypertension, IV hydralazine should be administered as an initial dose of 10 mg via slow IV infusion, with a maximum initial dose of 20 mg, and repeated every 4–6 h as needed. The dosing of IV hydralazine is crucial in managing severe hypertension, and according to 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, the recommended dosing is an initial 10 mg via slow IV infusion. Key points to consider when administering IV hydralazine include:

• The initial dose should not exceed 20 mg, and the medication should be repeated every 4–6 h as needed, based on the patient's blood pressure response.
• The onset of action occurs within 10–30 min, and the fall in blood pressure lasts 2–4 h, as noted in the guideline 1.
• Hydralazine works as a direct arterial vasodilator, causing relaxation of vascular smooth muscle and reducing peripheral resistance, which can lead to reflex tachycardia.
• Caution is warranted in patients with coronary artery disease, as the reflex sympathetic stimulation may increase myocardial oxygen demand.
• Lower initial doses may be recommended for elderly patients or those with renal impairment, although specific dose adjustments are not provided in the guideline 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 Certain patients (especially those with marked renal damage) may require a lower dose.

The recommended dosing for intravenous (IV) hydralazine for managing severe hypertension is 20 to 40 mg, repeated as necessary, with frequent blood pressure checks. Certain patients, such as those with marked renal damage, may require a lower dose 2.

From the Research

IV Hydralazine Dosing

• The recommended dosing for intravenous (IV) hydralazine for managing severe hypertension is not explicitly stated in the provided studies, but the studies provide information on the dosing used in various clinical trials.
• In one study 3, IV hydralazine was administered at a slow rate of 5 mg for five minutes, repeated every 20 minutes (maximum of five doses) until a blood pressure of ≤150/100 mmHg was achieved.
• Another study 4 reported a mean dose of 11.4 ± 4.3 mg of IV hydralazine, but did not provide information on the dosing frequency or duration.
• A study from 1983 5 evaluated the acute pulmonary and systemic haemodynamic response to low (0.15 mg/kg) and high (0.30 mg/kg) doses of intravenous hydralazine in patients with severe pulmonary hypertension.

Efficacy of IV Hydralazine

• IV hydralazine has been shown to be effective in reducing blood pressure in patients with severe hypertension.
• One study 6 found that treatment with IV hydralazine led to a significant reduction in mean arterial pressure (MAP), systolic blood pressure (SBP), and diastolic blood pressure (DBP) compared to no treatment.
• Another study 3 found that IV hydralazine achieved the target blood pressure in an average time of 45.80 +/- 25.17 minutes, and required an average of 1.72 +/- 0.904 doses.

Safety and Adverse Effects

• IV hydralazine has been associated with adverse effects, including hypotension, which was reported in 11 patients in one study 4.
• Another study 3 found that IV hydralazine was associated with more maternal adverse effects compared to IV labetalol, although these effects were not severe enough to warrant discontinuation of the medication.