💊 Ondansetron

5-HT₃ Receptor Antagonist Antiemetic

Generic Name	Ondansetron
Drug Class	Selective 5-HT₃ Receptor Antagonist
Indications	Prevention and treatment of nausea and vomiting Chemotherapy-induced nausea and vomiting (CINV) Post-operative nausea and vomiting (PONV) Acute gastroenteritis-related vomiting
Mechanism of Action	Selectively blocks serotonin (5-HT₃) receptors in the chemoreceptor trigger zone and gastrointestinal tract, preventing initiation of the vomiting reflex.
Available Forms & Strengths	• Tablet: 4 mg, 8 mg • Oral solution • Injection: 2 mg/mL • Orally disintegrating tablet (ODT)
Dosage	Adults: 4–8 mg every 8–12 hours Children: 0.15 mg/kg per dose (max 8 mg)
Route	Oral, IV, IM
Common Side Effects	Headache Constipation Dizziness Fatigue
Serious Adverse Effects	QT prolongation, arrhythmia, serotonin syndrome (rare)
Contraindications	Hypersensitivity to ondansetron or other 5-HT₃ antagonists
Precautions	• Congenital long QT syndrome • Electrolyte imbalance • Hepatic impairment
Drug Interactions	• Other QT-prolonging drugs • SSRIs / SNRIs (↑ serotonin syndrome risk)
Pregnancy & Lactation	Pregnancy: Generally considered safe Lactation: Use with caution
Storage	Store below 30°C, protect from light
References	BNF for Children \| Nelson Textbook of Pediatrics \| Manufacturer Information

⚠️ Clinical note: Use lowest effective dose and monitor ECG in patients at risk of QT prolongation.