Abstract

These chemically related drugs lower the blood pressure by blocking adrenergic neurones, and their effects resemble those of guanethidine and bretylium. Concurrent administration of a thiazide diuretic potentiates each of these drugs, thus allowing the dose to be reduced. As might be expected the greatest reduction in blood pressure normally occurs in the standing position, but symptoms of hypotension, such as faintness, giddiness and weakness occur if the dose is excessive or under conditions which potentiate the effect of adrenergic blockade, for example, on first rising from bed, in a hot environment, during and after exercise, and after blood loss. Other symptoms caused by adrenergic blockade, such as nasal stuffiness and failure of ejaculation are common. Impotence has been reported.