Urapidil: Alpha-1 Blocker and 5-HT1A Agonist for Hypertensive Crisis
Urapidil (Ebrantil) is a combined alpha-1 adrenergic receptor blocker and 5-HT1A serotonin receptor agonist. The peripheral alpha-1 blockade reduces vasoconstriction, while the central 5-HT1A agonism activates vasomotor centres in the brainstem, preventing the reflex tachycardia typically seen with pure vasodilators.
Primarily used intravenously for hypertensive crises and perioperative blood pressure control, and orally for difficult-to-control hypertension unresponsive to other agents.
Mechanism of Action
Peripheral: competitive alpha-1 receptor blockade reduces systemic vascular resistance. Central: 5-HT1A agonism in the brainstem vasomotor centre reduces sympathetic outflow, moderating the blood pressure lowering to prevent excessive drops and avoiding reflex tachycardia. This dual mechanism provides smooth, controlled blood pressure reduction.
Indications & Use
IV: hypertensive crisis/emergency (rapid BP reduction required), perioperative hypertension, hypertensive encephalopathy. Oral: treatment-resistant hypertension as add-on therapy when other agents are insufficient.
Dosage
IV (crisis): initial 10–50 mg slow IV bolus; maintenance infusion 9–30 mg/hour. Oral: 30–90 mg twice daily. Reduce oral dose in elderly and renal impairment. Monitor BP closely during IV administration.
Side Effects
Common: dizziness, fatigue, nausea, headache. Orthostatic hypotension (less than with pure alpha-blockers). Reflex tachycardia minimal due to central 5-HT1A mechanism. First-dose effect with oral therapy.
Drug Interactions
Other antihypertensives: additive hypotensive effect. Cimetidine: increases urapidil plasma levels. Alcohol: potentiates hypotension. PDE-5 inhibitors (sildenafil): enhanced hypotension.
Contraindications
Aortic isthmus stenosis (coarctation), arteriovenous shunts with haemodynamic significance, hypersensitivity. Caution in severe hepatic impairment and elderly.
Frequently Asked Questions
Why does urapidil not cause as much reflex tachycardia as other vasodilators?
The central 5-HT1A agonism in the brainstem vasomotor centre counters the reflex sympathetic activation that would normally cause tachycardia. This makes urapidil better tolerated in acute settings compared to pure vasodilators like hydralazine.
How quickly does IV urapidil work?
IV urapidil begins lowering blood pressure within 2–5 minutes, with peak effect at 15 minutes. This rapid onset makes it suitable for hypertensive emergencies requiring fast, controllable BP reduction.
Can urapidil be used in pregnancy?
Urapidil is not a first-choice antihypertensive in pregnancy. The preferred agents for pregnancy-related hypertensive crisis include labetalol IV, hydralazine IV, and nifedipine oral. Consult obstetric guidelines for specific recommendations.
References
- ESC Guidelines on Hypertensive Emergencies
- EMA product information Ebrantil
- Deutsche Gesellschaft für Anästhesiologie perioperative Hypertension
Medical Disclaimer: This information is for educational purposes only and does not replace professional medical advice.