Hexamethonium is a ganglionic blocker, a neuronal nAch (NN) receptor antagonist which acts in autonomic ganglia by binding mostly in or on the NN receptor, and not the acetylcholine binding site itself. It has no effect on the muscarinic acetylcholine receptors (mAChR) located on target organs of the parasympathetic nervous system, nor the nicotinic acetylcholine receptors at the neuromuscular junction (NM) that are responsible for skeletal muscle motor response.
The organ system and adverse effects of ganglion blockers are because both the parasympathetic and sympathetic stimuli are blocked at the preganglionic sites. Side effects include combined sympatholytic (e.g. orthostatic hypotension and sexual dysfunction) and parasympatholytic effects (e.g. constipation, urinary retention, glaucoma, blurry vision, decreased lacrymal secretion, dry mouth (xerostomia) effects.
The use of hexamethonium, an unapproved drug, in a normal volunteer during a medical study is believed to have caused her death.