MECHANISM
OF ACTION OF IRRITANT DRUGS
With
the advancement in molecular pharmacology, the mechanism of action of drugs
have been elucidated at the level of receptors, enzymes and genes. Irritant
drugs, on the other hand, act by local mechanism, and by their irritant and stimulant
action on nerves, mucosal epithelium or muscle fibres produce effects which can
be best understood with some examples.
·
Purgatives like bisacodyl, sodium
picosulphate etc irritate the mucosa and stimulate the myenteric neurones,
resulting in increased watery secretion and vigorous muscle contractions of the
gut wall.
·
Capsaicin, a component of chili, is a
chemical irritant and acts on peripheral nerves. It is used for relief of pain
in muscles and joints in arthritis, sprain and injury.
·
Certain chemicals which when introduced
intrauterine can cause vigorous uterine contractions and abortion by irritant
action. It is misused by miscreants for illegal abortion.
·
Ipecacuanha: The dried root of Cephaeliv
ipecacuanha contains emetine and is used as syrup ipecac for inducing vomiting.
It acts by irritating gastric mucosa as well as through CTZ.
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