5-HT3 ANTAGONIST...
EXAMPLES: Ondansetron, granisetron.
MECHANISMOF ACTION: Selective 5-HT3 receptor antagonists that act peripherally on vagal
nerve endings of the GI tract and centrally in the CTZ. 5-HT3 receptors in the CTZ in the area
postrema of the medulla contribute to the perception of nausea and the control of vomiting.
- Post-operative nausea and vomiting (PONV).
- Nausea and vomiting associated with cytotoxic drugs (chemotherapy) and radiotherapy.
- Prolonged QT interval and cardiac conduction defects.
- Hypersensitivity.
- GI disturbance (especially constipation due to increased large bowel transit time).
- Headache.
- Flushing.
- Metabolised predominantly in the liver. t½ for ondansetron and granisetron is ~5 h.
- No specific drug monitoring required.
- Effects reduced by drugs that induce liver enzymes (phenytoin, carbamazepine, rifampicin).
- Increased risk of torsades de pointes with other drugs that prolong the QT interval.
- Establish a cause for emesis prior to prescribing an anti-emetic.
- Very effective anti-emetic agents, particularly for PONV.
- Careful monitoring of symptoms if these drugs are used in patients with subacute bowel obstruction due to effects on large bowel motility.
Tags:
Pharmacology