Hexamethonium is a non-depolarising ganglionic blocker, a neuronal nicotinic ( nAChR)

receptor antagonist A receptor antagonist is a type of receptor ligand or drug that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist. Antagonist drugs interfere in the natural operation of rec ...

that acts in autonomic ganglia by binding mostly in or on the nAChR receptor, and not the

acetylcholine Acetylcholine (ACh) is an organic compound that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Par ...

binding site itself. It does not have any effect on the muscarinic acetylcholine receptors ( mAChR) located on target organs of the

parasympathetic nervous system The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The autonomic nervous system is responsible for regulat ...

, nor on the nicotinic receptors at the skeletal neuromuscular junction, but acts as antagonist at the nicotinic acetylcholine receptors located in sympathetic and parasympathetic ganglia ( nAChR).

Pharmacology

By blocking the neuronal nicotinic receptors in autonomic ganglia, which are necessary for transmission in all autonomic ganglia, both the sympathetic and parasympathetic nervous systems are inhibited. Its action on the neuronal nicotinic receptors is primarily through the block of the ion pore, rather than through competition with the binding site for acetylcholine. Postganglionic sympathetic systems are usually regulated by

norepinephrine Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic compound, organic chemical in the catecholamine family that functions in the brain and human body, body as a hormone, neurotransmitter and neuromodulator. The ...

(noradrenaline) (adrenergic receptors), whereas parasympathetic systems are acetylcholine-based, and instead rely on muscarinic receptors (some post-ganglionic sympathetic neurons, such as those stimulating sweat glands, release acetylcholine). The organ system and adverse effects of ganglion blockers are due to the parasympathetic and sympathetic stimuli blockage at preganglionic sites. Side-effects include combined sympatholytic (e.g., orthostatic hypotension and

sexual dysfunction Sexual dysfunction is difficulty experienced by an individual or partners during any stage of normal sexual activity, including physical pleasure, desire, preference, arousal, or orgasm. The World Health Organization defines sexual dysfunction ...

) and parasympatholytic (e.g., constipation,

urinary retention Urinary retention is an inability to completely empty the bladder. Onset can be sudden or gradual. When of sudden onset, symptoms include an inability to urinate and lower abdominal pain. When of gradual onset, symptoms may include urinary incont ...

glaucoma Glaucoma is a group of eye diseases that can lead to damage of the optic nerve. The optic nerve transmits visual information from the eye to the brain. Glaucoma may cause vision loss if left untreated. It has been called the "silent thief of ...

, blurry vision, decreased lacrimal gland secretion, dry mouth ( xerostomia) effects.

Uses

It was formerly used to treat disorders, such as chronic

hypertension Hypertension, also known as high blood pressure, is a Chronic condition, long-term Disease, medical condition in which the blood pressure in the artery, arteries is persistently elevated. High blood pressure usually does not cause symptoms i ...

, of the

peripheral nervous system The peripheral nervous system (PNS) is one of two components that make up the nervous system of Bilateria, bilateral animals, with the other part being the central nervous system (CNS). The PNS consists of nerves and ganglia, which lie outside t ...

, which is innervated only by the

sympathetic nervous system The sympathetic nervous system (SNS or SANS, sympathetic autonomic nervous system, to differentiate it from the somatic nervous system) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous sy ...

. The non-specificity of this treatment led to discontinuing its use. The use of inhaled hexamethonium, an unapproved drug, in a normal volunteer during a medical study is believed to have caused or contributed to her death in light of the presence of abnormal "ground glass opacities" on her chest X-ray.

References

{{Nicotinic acetylcholine receptor modulators Nicotinic antagonists Quaternary ammonium compounds

Pharmacology

Uses

See also

References