Drug Index



Mechanism :

Ondansetron is a selective 5-HT3 receptor antagonist. While its mechanism of action has not been fully characterized, ondansetron is not a dopamine-receptor antagonist. Serotonin receptors of the 5-HT3 type are present both peripherally on vagal nerve terminals and centrally in the chemoreceptor trigger zone of the area postrema. It is not certain whether ondansetron antiemetic action is mediated centrally, peripherally, or in both sites.

Indication :

• Chemotherapy induced nausea and vomiting

• Post-operative nausea and vomiting

Contraindications :

Contraindicated for patients known to have hypersensitivity to the drug.

Dosing :

Nausea and vomiting chemotherapy induced:


4-12 years: 4 mg started half hour before chemotherapy, then 4 and 8 hours after first dose, then 3 times a day for 1-2 days after chemotherapy.

>12 years: 8 mg started half hour before chemotherapy, then 2 times a day for 1-2 days after chemotherapy or a single dose of 24 mg.


>6 months: 0.15 mg/kg over 15 mins, given half hour before chemotherapy, then 4 and 8 hours after first dose. Max: 16 mg per dose.

Post-op nausea and vomiting:

Give slow IV slow infusion.

1 month-12 years: 0.1 mg/kg in <40 kg and 4 mg in >40 kg.

12-18 years: 4 mg before anaesthesia or after procedure (IV/IM)

OR, 16 mg 1 hour before anesthesia orally.

Adverse Effect :

Commonly reported adverse reactions include headache, malaise, fatigue, constipation and diarrhea.

Interaction :

Phenytoin, Carbamazepine, and Rifampicin: The clearance of ondansetron was significantly increased, and ondansetron blood concentrations were decreased.

03/10/2020 17:43:53 Ondansetron
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