Selective Inhibition of the Sympathetic Nervous System in Man with Bretylium Tosylate, a New Antihypertensive Agent

BOURA and his associates have denmon- strated that bretylium tosylate (Daren- thin) * produces a selective block of the sympathetic nervous system.'This beiizyl quaternary ammoniium compound appears to accumulate preferentially in peripheral sym- pathetic neurones.Unlike adrenergic blocking agents the effects of released or injected epi- nephrine and norepinephrine are not antagonized, and unlike ganglion-blocking drugs the parasympathetic nervous system is not inihibited at therapeutic dose levels of bretylium.1 Clinical trials in hypertensive patients indi- cate that orally administered bretylium tosyl- ate causes a predominantly orthostatic fall of blood pressure comparable to that achieved with the ganglion-blocking drugs but without the side effects of parasympathetic blockade.2The following report summarizes our experi- ence to date with this new agent. Inhibition of Sympathetic VasoconstrictorReflexes The reflex activity of the sympathetic vaso- constrictor system was assessed in normotensive men as follows: 1.The Valsalva "overshoot" of arterial pressure was recorded directly with a strain gage from a needle placed in the brachial artery.After a deep inspiration the subject blew forcefully and steadily into a closed tube for 10 seconds to produce a sustained increase in intrathoracie pressure.The expiratory effort was then suddenly and completely released.The resulting "overshoot" of arterial pressure has been