Hydralazine is a direct-acting vasodilator used to treat hypertension and heart failure. Learn about its mechanism of action, dosage, side effects, brand names, price, and clinical uses.
Table of Contents:
1. Introduction
3. Pharmacokinetics and Dynamics
4. Indications & Drug of Choice
5. Contraindications
6. Side Effects
7. Drug Interactions
8. Dosage
9. Brand Names
10. Price
11. Conclusion
1. Introduction:
*Hydralazine* is a *direct-acting arterial vasodilator* primarily used in the management of *moderate to severe hypertension* and *heart failure*, especially in combination with nitrates in specific populations. It relaxes vascular smooth muscle, reducing systemic resistance.
2. Mechanism of Action:
Hydralazine works by *directly relaxing the smooth muscle* in arterioles (not veins), which leads to:
- ↓ Peripheral vascular resistance
- ↓ Blood pressure
- ↑ Heart rate and cardiac output (reflex sympathetic activation)
It also *stimulates nitric oxide release*, contributing to its vasodilatory effect.
3. Pharmacokinetics and Dynamics:
| Absorption | Rapid (oral)
| Onset | 20–30 minutes (oral), 5–20 min (IV)
| Half-life | 2–8 hours
| Metabolism | Hepatic (acetylation – genetically variable)
| Excretion | Urine
*Note:* Slow acetylators may have higher plasma levels and increased side effects.
4. Indications & Drug of Choice:
- *Severe or resistant hypertension*
- *Hypertensive emergency in pregnancy (pre-eclampsia/eclampsia)*
- *Heart failure* (especially in Black patients, with nitrates)
Drug of Choice for:
- *Hypertensive crisis in pregnancy*
- *Alternative in heart failure when ACE inhibitors are not tolerated*
5. Contraindications:
- Rheumatic heart disease involving the mitral valve
- Hypersensitivity to hydralazine
- Aortic aneurysm/dissection (due to reflex tachycardia risk)
6. Side Effects:
- Headache
- *Lupus-like syndrome* (especially with prolonged use at high doses)
- Nausea, vomiting
7. Drug Interactions:
- *Beta-blockers:* Often co-administered to prevent reflex tachycardia
- *Diuretics:* Help manage sodium/fluid retention
- *MAO inhibitors:* Risk of severe hypotension
- *Other antihypertensives:* Additive effects may lead to hypotension
8. Dosage:
*For Hypertension:*
- Oral: Start with *10–25 mg 2 to 4 times daily*, max dose *200–300 mg/day*
- IV (in emergencies): *5–10 mg IV every 20–30 minutes*, or continuous infusion
For Heart Failure:
- Usually *25–75 mg* orally 3–4 times daily, often in combination with isosorbide dinitrate
*Pregnancy-Induced Hypertension:*
- IV 5 mg every 15–20 minutes as needed
9. Brand Names:
- *Apresoline*
- *Hydral*
- *Nepresol*
- *Dralon*
- *Hydrall*
10. Price:
- *USA:* $10–30/month (generic)
- *India/Pakistan:* Rs. 5–10 per tablet (25 mg)
Available in *tablets and injectable forms*
11. Conclusion:
*Hydralazine* remains an effective and affordable option for managing *hypertension* and *heart failure*, especially in patients who cannot tolerate ACE inhibitors. Monitoring for lupus-like symptoms and combining it with beta-blockers and diuretics is often necessary to minimize side effects and enhance efficacy.
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