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’s antiemetic action is mediated centrally, peripherally, or in both sites. However, cytotoxic chemotherapy appears to be associated with release of serotonin from the enterochromaffin cells of the small intestine.

Dantron Tablet: Each film coated tablet contains Ondansetron Hydrochloride Dihydrate BP 9.977 mg equivalent to Ondansetron 8 mg. Dantron Syrup: Each 5 ml syrup contains Ondansetron Hydrochloride Dihydrate BP equivalent to Ondansetron 4 mg.
1. Prevention of nausea and vomiting associated with highly emetogenic cancer chemotherapy, including Cisplatin ≥ 50 mg/m2 2. Prevention of nausea and vomiting associated with initial and repeat courses of moderately emetogenic cancer chemotherapy 3. Prevention of nausea and vomiting associated with radiotherapy in patients receiving either total body irradiation, single high-dose fraction to the abdomen, or daily fractions to the abdomen 4. Prevention of post-operative nausea and/or vomiting 5. Nausea-vomiting associated with pregnancy 6. Nausea-vomiting associated with gastroenteritis
Nausea-vomiting in gastroenteritis Adult: 8 mg three times daily. Pediatric (1 month or over): 0.15 mg/kg body weight three times daily. Nausea vomiting in pregnancy  8 mg (1 tablet) 2-3 times daily
Ondansetron is contraindicated for patients known to have hypersensitivity to the drug.
Ondansetron is not a drug that stimulates gastric or intestinal peristalsis. It should not be used instead of nasogastric suction. The use of Ondansetron in patients following abdominal surgery or in patients with chemotherapy-induced nausea and vomiting may mask a progressive ileus and/or gastric distension.
Generally Ondansetron is well tolerated. However few side effects including headache, diarrhoea, fatigue, dizziness and constipation may be seen after Ondansetron is administered.
The following drugs should be used with caution when concomitantly used with Ondansetron: Phenytoin, Carbamazepine, Rifampicin & Tramadol.
Pregnancy: Pregnancy category B. Nursing mother: It is not known whether Ondansetron is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Ondansetron is administered to a nursing woman.
There is no specific antidote for Ondansetron overdose. Hypotension (and faintness) occurred in a patient that took 48 mg of Ondansetron tablets.
Dantron Tablet: Each box contains 3 blister strips of 10 tablets. Dantron Syrup: Each bottle contains 50 ml Syrup.