This article needs attention from an expert in Pharmacology.August 2015)(
A ganglionic blocker (or ganglioplegic) is a type of medication that inhibits transmission between preganglionic and postganglionic neurons in the Autonomic Nervous System, often by acting as a nicotinic receptor antagonist. Nicotinic acetylcholine receptors are found on skeletal muscle, but also within the route of transmission for the parasympathetic and sympathetic nervous system (which together comprise the autonomic nervous system). More specifically, nicotinic receptors are found within the ganglia of the autonomic nervous system, allowing outgoing signals to be transmitted from the presynaptic to the postsynaptic cells. Thus, for example, blocking nicotinic acetylcholine receptors blocks both sympathetic (excitatory) and parasympathetic (calming) stimulation of the heart. The nicotinic antagonist hexamethonium, for example, does this by blocking the transmission of outgoing signals across the autonomic ganglia at the postsynaptic nicotinic acetylcholine receptor.
The opposite of a ganglionic blocker is referred to as a ganglionic stimulant. Some substances can exhibit both stimulating and blocking effects on autonomic ganglia, depending on dosage and/or duration of action. An example for such a "dual" action is nicotine, which does this via depolarization block (see classification below).
Nicotinic receptor antagonists:
Nicotinic receptor agonists (acting through depolarization block):
Blocking ACh release in autonomic ganglia (although these have many other actions elsewhere):
Ganglionic blockers are used less frequently now than they were in the past, because antihypertensives with fewer side effects are now available. Hexamethonium has been described as the "first effective antihypertensive drug". However, they are still used in some emergency situations, such as aortic dissection or autonomic dysreflexia.
- Cardiovascular: Orthostatic hypotension with or without reflex tachycardia
- ENT/glands: xerostomia, dry eyes, blurred vision, reduced bronchial secretion, hypohidrosis
- GIT: gastroparesis, constipation, urinary retention
- Sexual dysfunction: failure of erection and ejaculation
- in overdose risk of peripheral circulatory collapse (shock) and paralytic ileus
- Ganglionic+blockers at the US National Library of Medicine Medical Subject Headings (MeSH)
- "PHARMACOLOGY OF GANGLIONIC TRANSMISSION, 1998". Archived from the original on 2008-05-01. Retrieved 2008-10-04.
- Drill's Pharmacology in Medicine, 4th Ed. (1971). J. R. DiPalma (Ed.), pp. 723-724, New York: McGraw-Hill.
- Rang, H.P.; et al. (2012). Rang and Dale's Pharmacology. Elsevier. pp. 161–163. ISBN 9780702034718.
- Grossman, Ehud; Messerli, Franz H. (2007). "Hypertensive Urgencies and Emergencies". Comprehensive Hypertension. pp. 761–774. doi:10.1016/B978-0-323-03961-1.50066-0. ISBN 9780323039611.