From the Guidelines
Hydralazine should be prescribed at a dose of 100-200 mg total daily dose, divided into 2-4 doses, with a maximum daily dose of 300 mg, and should be used in combination with a beta-blocker and a diuretic to prevent reflex tachycardia and fluid retention, as recommended by the 2018 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 dosage and usage of hydralazine for treating hypertension can vary depending on the patient's response and medical history.
- The initial dose is typically 10 mg four times daily for the first 2-4 days, then increased to 25 mg four times daily for the remainder of the first week.
- The dose can be gradually increased to 50 mg four times daily in the second week if needed.
- Most patients require 100-200 mg total daily dose, divided into 2-4 doses, with a maximum daily dose of 300 mg.
- For hospitalized patients requiring rapid blood pressure control, hydralazine can be given intravenously at 10-20 mg doses every 4-6 hours as needed. Hydralazine works by directly relaxing vascular smooth muscle, primarily in arterioles, leading to decreased peripheral resistance and blood pressure reduction.
- It's often combined with a beta-blocker to prevent reflex tachycardia and with a diuretic to prevent fluid retention.
- Common side effects include headache, palpitations, and flushing.
- Long-term high-dose therapy (over 200 mg daily) may increase the risk of a lupus-like syndrome, so monitoring for symptoms like joint pain, fever, and rash is important, especially in slow acetylators and those with kidney disease, as noted in the 2018 resistant hypertension detection, evaluation, and management scientific statement from the American Heart Association 1. According to the 2024 ESC guidelines for the management of elevated blood pressure and hypertension, hydralazine should only be considered as a fifth-line treatment for resistant hypertension, after other medications such as spironolactone, eplerenone, and beta-blockers have been tried 1.
From the FDA Drug Label
DOSAGE AND ADMINISTRATION Initiate therapy in gradually increasing dosages; adjust according to individual response. Start with 10 mg four times daily for the first 2 to 4 days, increase to 25 mg four times daily for the balance of the first week. For the second and subsequent weeks, increase dosage to 50 mg four times daily. For maintenance, adjust dosage to the lowest effective levels. In a few resistant patients, up to 300 mg of hydrALAZINE hydrochloride tablets daily may be required for a significant antihypertensive effect.
The dosage of hydralazine for treating hypertension is as follows:
- Initial dosage: 10 mg four times daily for the first 2 to 4 days
- First week: 25 mg four times daily
- Second and subsequent weeks: 50 mg four times daily
- Maintenance: adjust dosage to the lowest effective levels
- Maximum dosage: up to 300 mg daily in resistant patients 2
From the Research
Hydralazine Dosage and Usage
- The dosage of hydralazine for treating hypertension is not explicitly stated in the provided studies, but it is mentioned that hydralazine was used in doses of up to 200 mg/day in one study 3.
- Hydralazine is a direct-acting vasodilator that has been used for the treatment of hypertension since the 1950s 4.
- The usage of hydralazine for treating hypertension is often in combination with other antihypertensive agents, such as beta-blockers and diuretics 5, 6, 3, 7.
Effects of Hydralazine on Hypertension
- Hydralazine has been shown to lower blood pressure in patients with hypertension, although its effect on clinical outcomes remains uncertain 4.
- Hydralazine increased plasma norepinephrine levels in patients with hypertension, indicating an increase in sympathetic activity 6.
- Hydralazine improved left ventricular diastolic function in patients with hypertension, but had no effect on left ventricular systolic function 6.
Comparison with Other Antihypertensive Agents
- Hydralazine was compared to nifedipine, a calcium antagonist, in several studies, and was found to have similar antihypertensive effects, but with different side effect profiles 6, 3, 7.
- Hydralazine was also compared to prazosin, an alpha-blocker, and was found to have similar antihypertensive effects, but with different side effect profiles 3.