Studies on tolerance to ganglionic blocking agents in man; reversal of depressor action of quaternary ammonium compounds

The hypotensive effects of intravenous injections of tetraethylammonium and hexamethonium chloride diminish and finally become pressor during the course of short-term treatment with subcutaneous hexamethonium. Evidence is presented to indicate that this "tolerance" is associated with a decreased sympathetic tone in the feet and forearm and is not due to increased amounts of circulating adrenal medullary or cortical hormones. Possibilities are discussed for this apparent vascular autonomy and the locus of vasoconstriction. Cross tolerance appeared between several ganglionic blocking agents tested and extended to a minor degree to adrenergic blocking agents.