Hydralazine

Drug Overview

Hydralazine is a direct-acting arterial vasodilator primarily used to control hypertension (high blood pressure) and related complications. This medication relaxes vascular smooth muscle, reduces peripheral vascular resistance, facilitates smoother blood flow, and thereby lowers blood pressure.

Clinically, hydralazine is also used to treat severe hypertensive crises and preeclampsia or eclampsia symptoms during pregnancy. Its mechanism of action does not depend on the sympathetic nervous system, making it particularly valuable for patients who respond poorly to other antihypertensive drugs.

Brand Names and Generic Name

The generic name of this drug is Hydralazine hydrochloride. Common brand names include Apresoline®. In Taiwan and Hong Kong, this medication is usually supplied in its generic form and requires a prescription from a physician.

Drug Classification

Hydralazine is classified as a direct arterial vasodilator, and it is considered a second-line treatment among antihypertensive medications. It is not a calcium channel blocker or ACE inhibitor, and its unique mechanism of action is typically reserved for severe cases where other antihypertensives are insufficient.

Indications

Primarily used to treat severe hypertension, especially in emergency situations to rapidly lower blood pressure. It is also used to manage hypertensive complications during pregnancy, such as preeclampsia or eclampsia.

In some cases, this drug is combined with other antihypertensives to enhance efficacy, such as with diuretics or beta-blockers for resistant hypertension.

Common Side Effects

• Mild side effects: dizziness, headache, nausea, lower limb edema, palpitations
• Moderate side effects: skin flushing (flushing syndrome), lightheadedness, fatigue

Serious side effects require immediate medical attention: difficulty breathing, chest pain, jaundice (yellowing of the skin or eyes), skin rash or peeling, altered consciousness.

Warnings and Precautions

Contraindications: Patients allergic to hydralazine, those with severe heart failure, or active gastrointestinal ulcers should avoid use. Use during pregnancy should be cautious and only when necessary.

This medication carries a black box warning: long-term use may induce autoimmune responses, leading to drug-induced lupus erythematosus, characterized by joint pain, fever, and positive antinuclear antibodies.

Drug Interactions

• Concomitant use with beta-blockers may cause excessive blood pressure lowering and cardiac conduction abnormalities
• Use with corticosteroids or immunosuppressants may increase the risk of immune system abnormalities
• When combined with diuretics, monitor serum sodium and potassium levels

Dosage and Administration

The starting dose is usually 25-50 mg taken 2-3 times daily, adjusted based on blood pressure response. In hypertensive emergencies, intravenous administration may be required.

Take after meals to reduce gastrointestinal discomfort. Do not stop medication abruptly to prevent rebound hypertension. Elderly or patients with renal impairment should start with lower doses.

Missed Dose

If a dose is missed within 1-2 hours, take it immediately and adjust the next dose timing accordingly. If close to the next scheduled dose, skip the missed dose and resume normal timing. Never take a double dose at once.

Overdose

Overdose may lead to hypotension, fainting, or shock. Seek immediate medical attention, possibly requiring hospitalization and blood pressure support therapy.

Symptoms of poisoning include severe dizziness, blurred vision, and speech difficulties. Patients or caregivers should keep the medication bottle and bring it to the emergency room for reference.

Frequently Asked Questions

When taking hydrochlorothiazide, should it be taken at a fixed time with meals?

Hydrochlorothiazide is recommended to be taken at the same time each day to maintain stable drug levels, but the exact timing should follow the physician’s instructions. If a dose is missed, take it immediately; if close to the next dose, skip the missed dose and do not take a double dose. Taking it after meals can reduce gastrointestinal discomfort.

What are common side effects of hydrochlorothiazide, and how can they be alleviated?

Common side effects include dizziness, headache, and edema, often due to vasodilation or fluid metabolism changes. Mild symptoms can be improved by reducing salt intake or increasing fluid intake. If rash, palpitations, or severe edema occur, contact a doctor promptly, as dose adjustments or additional medications may be necessary.

What should be considered when combining hydrochlorothiazide with other antihypertensives like beta-blockers?

Combination with beta-blockers may enhance blood pressure reduction but requires careful monitoring to avoid excessive hypotension or shock. The physician will adjust doses based on cardiac function and blood pressure control. Patients should have regular follow-ups and report any symptoms accurately.

How should daily life be managed while taking hydrochlorothiazide?

Regular blood pressure monitoring is recommended, along with maintaining a routine of aerobic exercise (e.g., 30 minutes daily) and limiting high-sodium foods to enhance efficacy. During vigorous exercise or in hot environments, hydration is important to prevent dehydration or electrolyte imbalance caused by diuretic effects.

Is hydrochlorothiazide suitable for patients with diabetes or renal impairment?

Hydrochlorothiazide may affect blood glucose and sodium levels. Diabetic patients should monitor blood sugar regularly and adjust antidiabetic medications as needed. Patients with renal impairment should adjust doses or choose other diuretics; the physician will evaluate safety based on glomerular filtration rate (GFR). Patients should inform their healthcare provider of their medical history.