Hydralazine

 Hydralazine – Full Introduction

Hydralazine is a direct-acting vasodilator primarily used in the treatment of hypertension and heart failure. It relaxes arterial smooth muscle, leading to a reduction in systemic vascular resistance and blood pressure. Hydralazine is often reserved for moderate to severe or resistant hypertension.

Drug Class

• Direct-Acting Vasodilator

Mechanism of Action

Hydralazine acts directly on arteriolar smooth muscle, causing:

• Arterial vasodilation (minimal effect on veins)

• Decreased peripheral vascular resistance

• Reduced afterload

• Increased cardiac output

The exact mechanism is not fully understood but involves interference with calcium metabolism and nitric oxide–mediated pathways.

Therapeutic Uses

• Hypertension (especially severe or resistant cases)

• Hypertensive emergencies (IV hydralazine)

• Heart failure (in combination with nitrates, especially in Black patients)

• Hypertension in pregnancy (pre-eclampsia, eclampsia)

Benefits

• Potent arterial vasodilator

• Useful in pregnancy (safer than many alternatives)

• Improves survival in heart failure when combined with nitrates

• Rapid blood pressure reduction (IV form)

Common Side Effects

• Headache

• Flushing

• Palpitations

• Tachycardia

• Fluid retention

Serious but Rare Side Effects

• Drug-induced lupus erythematosus (long-term use)

• Peripheral neuropathy

• Severe hypotension

• Myocardial ischemia

Contraindications & Precautions

• Coronary artery disease

• Rheumatic heart disease (mitral valve involvement)

• Systemic lupus erythematosus (use with caution)

• Often combined with beta-blockers and diuretics to reduce reflex tachycardia and fluid retention

Conclusion

Hydralazine is an effective direct vasodilator used mainly in resistant hypertension, hypertensive emergencies, and heart failure. Despite its side effects, it remains an important drug when carefully monitored and appropriately combined with other therapies.