Ketanserin: haemodynamic effects and mechanism of action.

The haemodynamic effects of ketanserin, a compound with S2-serotonergic receptor and alpha 1-adrenoceptor blocking properties, are reviewed in patients with essential hypertension. The drug has a definite antihypertensive action, both acutely and chronically, and its haemodynamic profile is similar to that of a vasodilator acting on both arterioles and veins but with its main action on arterioles. Its vasodilator action is associated with little reflex cardiostimulation. Pressor responses to i.v. phenylephrine are not altered by therapeutic i.v. doses of ketanserin but pressor responses to methoxamine, a compound that is more specific for vascular alpha 1-receptors than phenylephrine, have been reported to be reduced after chronic oral treatment with ketanserin. However, chronic ketanserin, unlike the alpha 1-adrenoceptor antagonist, prazosin in therapeutic doses, caused no parallel shift of the dose-pressor response curve of methoxamine and the shift was very small compared with prazosin. Studies in patients with autonomic failure and virtually no endogenous alpha 1-adrenergic tone have substantiated that ketanserin is capable of lowering blood pressure independently of alpha 1-adrenoceptor blockade.