Hello awesomites ! Today I am gonna talk about a drug named as "Metoclopramide".
Basically it's a anti-emetic drug.First let us know what is emesis !.In simple words emesis means vomiting.Chemoreceptor trigger zone (CTZ) is located in area postrema and the nucleus tractus solitarius (NTS) of medulla oblongata.They both act as a important relay areas for afferent impulses arising in g.i.t.,throat and other viscera.
Metoclopramide is a Pro kinetic drug
It acts on GIT causing increase in peristaltic movement with relaxation of pylorus .
Mechanism of action includes :
a)D2 antagonism:It Decreases dopamine concentration and obviously acetylcholine concentration increases !.Which causes activation of ACh receptors leading to increase in LES tone and gastric pressure .
b)5-HT4 agonism:Activates 5-HT4 receptors on primary afferent neurons (PAN) of the ENS,via excitatory interneurons.
Gastric hurrying and LES tonic effects are mainly due to this action which is synergised by bethanechol and attenuated by atropine .
c)5-HT3 antagonism: At high concentrations it can block 5-HT3 receptors present on inhibitory myenteric interneurons and in NTS/CTZ .Increase in ACh concentration is also seen in minor condition
Long term use can cause parkinsonism-since decrease in dopamine , galactorrhea and gynecomastia .
It hastens use of many drugs like aspirin and diazepam by its action
~Jaskunwar Singh & Ojas