Prazosin partly blocks clonidine-induced hypotension in patients with essential hypertension.

Prazosin has been reported to reduce the hypotensive and/or bradycardic effect of clonidine in various animal models. Investigations in humans have given conflicting conclusions about the effectiveness of the combination of clonidine and prazosin. In patients with essential hypertension prazosin significantly reduced the hypotensive effect of intravenous clonidine, but it failed to affect the clonidine-induced bradycardia. This finding means that the combination of prazosin and clonidine is inappropriate in antihypertensive therapy.