GI Motility - Pro Kinetic Agents Flashcards
What is the immediate mediator of smooth muscle contractility?
Acetylcholine
Which drug can act as an agonist at the 5HT-4 receptors to enhance gastric motility?
Cisapride
Which muscarinic agonist can stimulate M2 and M3?
Bethanechol
How would you block motility?
Anti-cholinergic agent since they cause constipation
Are D2 agonists Pro or Anti motility?
Anti-motility because they inhibit the release of acetylcholine
Which D2 antagonist (prevents the actions of dopamine) is given to enhance motility (by inhibiting acetylcholine release)?
Metoclopramide
Which is a benzamide that enhances the motility of smooth muscle from the esophagus to the proximal small intestine and accelerates gastric emptying from the duodenum to the ileocecal valve?
Metoclopramide (Reglan)
What is the net effect of metoclopramide?
Accelerate gastric emptying and reduce reflux from the duodenum and the stomach into the esophagus
Which agent sensitizes muscarinic receptors on intestinal smooth muscle to the actions of acetylcholine?
Metoclopramide
Does metoclopramide cross the blood brain barrier?
Yes. It produces most of the CNS side effects characteristic of D2 receptor blockade such as anti-emesis, hyperprolactemia, breast tenderness, menstrual irregularities, and extrapyramidal syndrome at high doses
What is metoclopramide used for?
- Treatment of diabetic gastroparesis
- esophageal reflux
- nausea and vomiting including pregnancy and chemotherapy
Which D2 antagonist does not penetrate well into the CNS so its effects are confined to the periphery?
Domperidone (Motilium)
Which is a better anti-emetic, 5HT-3 antagonist such as Zofran or metoclopramide?
5HT-3 antagonist
Which agents inexplicably are not reduced by muscarinic cholinergic antagonists?
Domperidone (have the same effects on gastrointestinal motility than metoclopramide)
Which D2 antagonist produces hyperprolactemia at the anterior pituitary?
Domperidone, Metoclopramide
What is domperidone used for?
Same as metoclopramide including anti-emetic even though it does not cross the blood brain barrier
Which agent is used for compassionate use only?
Cisapride (Propulsid)
Which benzamide increases colonic motility and can cause diarrhea?
Cisapride
What blocks the gastrointestinal actions of metoclopramide and cisapride
Atropine
Does cisapride influence the concentration of prolactin or cause extrapyramidal symptoms?
No because it does not block the D2 receptor
Cisapride is metabolized by what enzyme?
CYP3A4
What is Cisapride used for?
Same as metoclopramide and domperidone with the advantage of none of the side effects associated with dopaminergic blockade. Used mainly for esophageal reflux
What drug interactions are seen with cisapride?
It prolongs the Q-T interval so it can cause ventricular fibrillation at high doses. Drugs metabolized by CYP3A4 are contraindicated (erythromycin, ketoconazole, nefazodone, grapefruit juice)
What should you ask a patient before switching them from erythromycin?
Ask them what they are using it for because it is not only an antibiotic but it is also used for diabetic gastroparesis
