Indoramin is a postsynaptic selective alpha 1-adrenoceptor antagonist used in the treatment of hypertension. In contrast to some other alpha-blockers, animal studies suggest that its blood pressure lowering effect results from relaxation of peripheral arterioles as a consequence of blockade of postsynaptic alpha 1-adrenoceptors. Furthermore, unlike some other alpha-blockers, this lowering of blood pressure is rarely associated with reflex tachycardia or postural hypotension. Therapeutic trials have shown indoramin to be effective in lowering blood pressure in all grades of hypertension: mild and moderate hypertension when used alone, but generally in combination with a thiazide diuretic, and in moderate to moderately severe hypertension when used in combination with a beta-blocker and diuretic. In a few small comparative studies, no significant difference was found in the blood pressure lowering effects between indoramin and methyldopa, propranolol and prazosin. Side effects were similar for indoramin, propranolol and methyldopa; however in the 1 comparative study with prazosin, prazosin produced a lower incidence of sedation. Indeed, the most common side effect with indoramin therapy has been sedation of a mild to moderate and/or transient nature, reported in about 19% of cases. Other side effects which have sometimes led to a withdrawal of indoramin treatment have been dry mouth, dizziness, and in males, failure of ejaculation; however, side effects may be reduced by starting therapy with smaller doses and titrating more gradually.
