What is the recommended use and dosage of Hydralazine (hydralazine) for treating hypertension?

From the Guidelines

Hydralazine is recommended for treating hypertension, typically as an add-on medication when first-line agents are insufficient, with a usual starting oral dose of 10 mg four times daily for the first 2-4 days, then increasing to 25 mg four times daily for the remainder of the first week, and a maximum daily dose of 300 mg. For adults with hypertension, the dose can be gradually increased to 50 mg four times daily in the second week if needed. Most patients require 100-200 mg daily divided into four doses. For hypertensive emergencies, hydralazine can be administered intravenously at 10-20 mg doses or intramuscularly at 10-50 mg doses, repeated as necessary, as stated in 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. Hydralazine works by directly relaxing vascular smooth muscle, primarily in arterioles, leading to decreased peripheral resistance and blood pressure reduction. Common side effects include headache, palpitations, and tachycardia due to reflex sympathetic activation. Long-term use requires monitoring for potential development of drug-induced lupus-like syndrome, particularly in slow acetylators. Hydralazine is often combined with a beta-blocker to counteract reflex tachycardia and with a diuretic to enhance its antihypertensive effect and reduce fluid retention, as recommended in the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline 1 and the 2018 executive summary 1.

Some key points to consider when using hydralazine include:

• The combination of hydralazine and nitrates is recommended to improve outcomes for patients self-described as African-Americans, with moderate-severe symptoms on optimal therapy with ACE inhibitors, beta blockers, and diuretics, as stated in the 2009 focused update: ACCF/AHA guidelines for the diagnosis and management of heart failure in adults 1.
• Hydralazine is associated with sodium and water retention and reflex tachycardia; use with a diuretic and beta blocker, as recommended in the 2018 executive summary 1.
• The target blood pressure is <130/80 mm Hg, but consideration should be given to lowering the blood pressure even further, to <120/80 mm Hg, as stated in the 2007 treatment of hypertension in the prevention and management of ischemic heart disease: a scientific statement from the American Heart Association Council for High Blood Pressure Research and the Councils on Clinical Cardiology and Epidemiology and Prevention 1.

Overall, hydralazine is a useful medication for treating hypertension, particularly in certain patient populations, and its use should be guided by the most recent and highest-quality evidence, such as the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline 1.

From the FDA Drug Label

The usual recommended oral starting dosage is 0.75 mg/kg of body weight daily in four divided doses. Dosage may be increased gradually over the next 3 to 4 weeks to a maximum of 7.5 mg/kg or 200 mg daily. The recommended use and dosage of Hydralazine for treating hypertension is:

• Oral dosage: 0.75 mg/kg of body weight daily in four divided doses, with a maximum of 7.5 mg/kg or 200 mg daily 2
• Parenteral dosage: 1.7 to 3.5 mg/kg of body weight daily, divided into four to six doses 3
• Intravenous bolus injection: 20 to 40 mg, repeated as necessary 3 Key points:
• Dosage may be increased gradually over the next 3 to 4 weeks
• Blood pressure should be checked frequently
• Certain patients (especially those with marked renal damage) may require a lower dose

From the Research

Recommended Use and Dosage of Hydralazine

The recommended use and dosage of hydralazine for treating hypertension vary depending on the specific condition being treated.

• For severe hypertension in pregnancy, hydralazine may be used, but its effectiveness and safety compared to other antihypertensives are still being studied 4.
• In cases of hypertensive crisis, intravenous hydralazine can be an alternative when rapid arterial pressure reduction is needed, with a typical dose of 5 mg 5.
• However, the use of intravenous hydralazine in hospitalized patients is often unjustified, and its administration can lead to hypotension and other adverse events 6.
• In severe preeclampsia, nifedipine may be a more effective and safer option than hydralazine for controlling blood pressure 7.

Dosage Considerations

• The dosage of hydralazine can range from 5-10 mg intravenously for severe hypertension 5 to higher doses for more severe cases.
• The frequency of administration and the total dose used can vary depending on the patient's response to treatment and the presence of any adverse effects.
• It is essential to monitor blood pressure and other vital signs closely when using hydralazine, especially in patients with severe hypertension or those who are pregnant 4, 7.

Safety and Efficacy

• Hydralazine can cause adverse effects such as hypotension, headache, and palpitations, especially when used in high doses or in combination with other antihypertensives 4, 6.
• The safety and efficacy of hydralazine in certain patient populations, such as those with severe hypertension or preeclampsia, are still being studied, and its use should be carefully considered and monitored 4, 7.