Vascular effects of etilefrine. Further studies to substantiate the predominant indirect sympathomimetic action of this agent.

The suggested use of etilefrine in the treatment of patients with orthostatic hypotension is based on the premise that it has an action similar to that of noradrenaline (Miller, Wiener and Bloomfield, 1973). However, earlier work from this laboratory (Frost, Frewin and Gerke, 1977; Frost, Frewin, Gerke and Downey, 1978; Frost, Halloran, Frewin, Gerke and Downey, 1978) on blood vessels in the rat tail has suggested that the drug acts predominantly as an indirect sympathomimetic agent. The present study examined the action of etilefrine on the central artery of the rabbit ear. This vessel is known to have a rich sympathetic innervation (de la Lande, Frewin and Waterson, 1967) and has the added advantage that it can be surgically denervated. It therefore became possible to examine the effects of etilefrine on both normal and denervated arteries and to quantitate the extent to which the drug relied on the symphathetic nerves for its vasoconstrictor effects.