[Drug clinics. Drug of the month. Irbesartan (Aprovel)].

Irbesartan is a novel AT1 subtype angiotensin II receptor antagonist. Blockade of AT1 receptors by irbesartan is not competitive, but "insurmountable". The drug inhibits in a significant dose-dependent manner the maximal contractile response that can be induced by angiotensin II in isolated strips of rabbit aorta. Even high doses of angiotensin II are unable to overcome the AT1 specific receptor blockade. The drug is directly active and requires no prior biotransformation. Its bioavaility after oral administration is excellent (60-80%) and is not altered by meals. The maximal hypotensive effect is measured 3-6 h after intake. The long half life (11-15 h) allows administration in one single daily dose. Irbesartan is registered in Belgium fot the treatment of essential arterial hypertension only. The hypotensive clinical effects, present from the start, become obvious after 1-2 weeks and maximal after 4-6 weeks. The usual daily dose is 150 mg. If needed, it can be increased up to 300 mg/day or, else, be decreased to 75 mg daily in the dialysed or aged patient. Side effects are negligible.