What is the use of Hydralazine (Apresoline)?

From the Guidelines

Hydralazine should be used with caution and is not the first-line agent for acute treatment of hypertensive emergencies due to its unpredictability of response and prolonged duration of action, 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.

Key Points

• Hydralazine is a direct-acting vasodilator medication used to treat high blood pressure and heart failure.
• The typical starting dose for hypertension is 10-25 mg orally four times daily, which can be gradually increased to 50 mg four times daily if needed.
• For heart failure, it's often prescribed in combination with nitrates (like isosorbide dinitrate) to reduce cardiac workload and improve heart function.
• Common side effects include headache, dizziness, flushing, palpitations, and nasal congestion.
• More serious concerns include a lupus-like syndrome with prolonged use at higher doses, particularly in slow acetylators.
• Hydralazine requires gradual dose titration to minimize side effects and should be taken consistently with respect to meals.
• It's particularly useful in hypertensive emergencies during pregnancy since it's considered relatively safe for the fetus.
• The medication works through direct relaxation of arteriolar smooth muscle, likely by interfering with calcium movement in the vascular cells, leading to decreased peripheral resistance without significantly affecting venous return.

Dosage and Administration

• Initial dose: 10 mg via slow IV infusion (maximum initial dose 20 mg) for hypertensive emergencies, as recommended in the 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline 1.
• Repeat every 4-6 hours as needed.

Special Considerations

• Hydralazine is not the first-line agent for acute treatment of hypertensive emergencies due to its unpredictability of response and prolonged duration of action 1.
• It's particularly useful in hypertensive emergencies during pregnancy since it's considered relatively safe for the fetus.
• 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 1.

From the FDA Drug Label

HydrALAZINE hydrochloride, USP, is an antihypertensive, for oral administration. The FDA drug label does not answer the question.

From the Research

Hydralazine Overview

• Hydralazine is a direct-acting vasodilator used for the treatment of hypertension since the 1950s 2
• It has largely been replaced by newer antihypertensive drugs with more acceptable tolerability profiles, but is still widely used in developing countries due to its lower cost 2

Mechanism of Action and Side Effects

• Hydralazine works by relaxing the muscles in blood vessel walls, which helps to lower blood pressure 2
• Some of the adverse effects related to hydralazine include reflex tachycardia, hemolytic anemia, vasculitis, glomerulonephritis, and a lupus-like syndrome 2

Clinical Use

• Hydralazine may be used in combination with other antihypertensive drugs, such as beta-blockers, diuretics, and angiotensin-converting enzyme inhibitors 3
• It is also used in the treatment of systolic heart failure, as part of a combination therapy that includes beta-blockers, angiotensin-converting enzyme inhibitors, and diuretics 3

Comparison with Other Antihypertensive Drugs

• Hydralazine is one of several classes of antihypertensive drugs, including beta-blockers, diuretics, calcium channel blockers, and angiotensin-converting enzyme inhibitors 4
• The choice of antihypertensive drug depends on the individual patient's needs and medical history, as well as the specific characteristics of the drug 5

Efficacy and Safety

• There is insufficient evidence to conclude on the effects of hydralazine versus placebo on mortality, morbidity, withdrawals due to adverse effects, serious adverse events, or systolic and diastolic blood pressure 2
• Hydralazine may reduce blood pressure when compared to placebo in patients with primary hypertension, but this data is based on before and after studies, not randomized controlled trials 2