Olcegepant, mechanism of action is:
Correct Answer: CGRP antagonist
Description: Ans. C. CGRP antagonistRef: Katzung's Basic and Clinical Pharmacology 13th/ed, p308Explanation# Calcitonin family of peptides includes:# Calcitonin# Calcitonin gene-related peptide (CGRP)# Adrenomedullin# Amylin# CGRP# Widely distributed: Largely in the C-cells of the thyroid gland, also found in CNS (central nervous system), PNS (peripheral nervous system), CVS (cardiovascular system), RS (respiratory system) and GIT (gastrointestinal tract).# CGRP-containing neuronal fibers are more abundant around arteries than around veins and in atria than in ventricles.# This peptide has vasodilatory property, in fact CGRP is the most potent vasodilator yet discovered.# When injected in systemic circulation, it causes hypotension and tachycardia.# When injected into CNS, it causes hypertension and suppression of feeding.# Release of CGRP from trigeminal nerves plays a central role in the pathophysiology of migraine. Selective serotonin agonist (triptans) normalizes CGRP levels.# CGRP antagonists though have not yet received FDA approval have shown promising results in trials for migraine. Antagonists developed are:- Olcegepant- Telcagepant# Note the name olcegepant: Calcitonin gene-related peptide antagonist.# These drugs are non-peptide antagonist.# Two primary hypotheses to explain the actions of antimigraine drugs are:# First, The triptans, ergot alkaloids, and antidepressants may activate 5-HT1D/1B receptors on presynaptic trigeminal nerve endings, thereby inhibiting the release of vasodilating peptides, (option b) and antiseizure agents may suppress excessive firing of these nerve endings (option d).# Second, the vasoconstrictor actions of direct 5-HT agonists (the triptans and ergot) may prevent vasodilation and stretching of the pain endings. It is possible that both mechanisms contribute in the case of some drugs.# Option a: Triptans (sumatriptan is 5 HT agonist).# Option b: CGRP itself is vasodilating peptide and olcegepant is CGRP antagonist. The triptans, ergot alkaloids, and antidepressants act by inhibiting the release of vasodilating peptides.# Option d: Antiseizure drugs like valproic acid and topiramate are useful in treatment of migraine, they reduce the excessive firing by trigeminal neurons.
Category:
Pharmacology
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