Ganglion Blocking Drugs

7/27/2019 Ganglion Blocking Drugs

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is a mass of nerve tissue

containing cell bodies ofneurons that is locatedoutside the central nervous

system.


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AUTONOMICGANGLIA LOCATIONSympathetic =>located near target

organs

=>consist of Celiac,

Hypogastric, Superiormesenteric and

Inferior mesenteric

Parasympathetic =>near target organsin the head (Ciliary,

Pterygopalatine,Submandibular andOtic)=>embedded in thewalls of target organsin the thorax,abdomen, and pelvis


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GANGLION-BLOCKING DRUGS


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Tetraethylammonium (TEA)

Hexamethonium

Mecamylamine

Trimethaphan


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absorption of quaternary ammonium (Hexamethomium,Tetraetylammonium) and sulfonium (Trimethaphan) from the

enteric tract is incomplete.

confined primarily to the extracellular space and are excretedmostly unchanged by the kidney.

MECAMYLAMINE:

=> a secondary amine, crosses both the blood brain,and placental barriers and well absorbed orally

=> concentrates in the liver and kidney,and excretedslowly in an unchanged form.

TRIMETHAPHAN: is inactive orally and is given by IV infusion.


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FIRST GROUP: characterized by

nicotine

stimulates ganglia andthen blocks them

causing a persistentdepolarization

Ex:

carbamoylcholinetetraethylammonium

SECOND GROUP: inhibit the postsynaptic

action of Ach nondepolarizing

blockade

Either:->by competing w/Ach for ganglionic

nicotinic receptor sites( Ex: Trimethaphan)->by blocking thechannel(Ex: Hexamethonium)


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SITE PREDOMINANT TONEEFFECT OF GANGLIONIC BLOCKADE

Arterioles Sympathetic (adrenergic) Vasodilation; increased peripheral bloodflow; hypotension

Veins Sympathetic (adrenergic) Dilation: peripheral pooling of blood;decreased venous return; decreasedcardiac output

Sweat glands Sympathetic (cholinergic) Anhidrosis (deficiency or absence ofperspiration)


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SITE PREDOMINANT TONE EFFECT OF GANGLIONIC BLOCKADE

Heart(S-A node)

Parasympathetic (cholinergic) Tachycardia

IrisParasympathetic (cholinergic) Mydriasis (dilation of the pupil)

Ciliary muscle

Parasympathetic (cholinergic) Cycloplegiafocus to far vision

Gastrointestinaltract

Parasympathetic (cholinergic) Reduced tone and motility; constipation;decreased gastric and pancreatic

secretions

Salivary glands Parasympathetic (cholinergic) Xerostomia (dry mouth )


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SITE PREDOMINANT TONE EFFECT OF GANGLIONIC BLOCKADE

Urinary bladder Parasympathetic (cholinergic)Urinary retention

Precipitate urinary retention in men

with prostatic hypoplasia.

Genital tract

Sympathetic (ejaculation) andparasympathetic (erection)

Decreased stimulation


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=> Many responses are undesirable effects that limit the therapeuticusefulness of these agents.

=>Are still important in pharmacological and physiological

research because of their ability to block autonomic ganglia.

MILD: Mydriasis

Dry mouth

Urinary hesistancy

Constipation Abdominal discomfort

Diarrhea

MORE SERIOUS: Hypotension Paralytic ileus Anginal pain


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MECAMYLAMINE (INVERSINE):

blocks central nicotinic receptor

reported effects: tremors, seizures and mentalconfusion

possible adjunct with the transdermal nicotinepatch to reduce nicotine craving in patients

attempting to quit smoking.

rarely used as an antihypertensive drugs


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TRIMETHAPHAN (ARFONAD):

is an extremely short-acting agent

used in the emergency treatment inhypertensive crisis due to direct vasodilatingproperties.

production of controlled hypotension incertain surgical procedures to reducebleeding.

Ganglion Blocking Drugs

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