Ondansetron 💊

📖 About

Always check the BNF link here.

• 💊 Ondansetron is a potent anti-emetic widely used in oncology, post-operative care, and palliative medicine.
• ✅ Particularly effective against chemotherapy- and radiotherapy-induced nausea and vomiting (CINV/RINV) and post-operative nausea/vomiting (PONV).

⚡ Mechanism of Action

• ⛔ 5-HT₃ receptor antagonist.
• Blocks serotonin receptors centrally in the chemoreceptor trigger zone (CTZ) and peripherally in the GI tract/vagus nerve.
• ⬇️ Prevents serotonin-mediated stimulation of vomiting pathways.

🩺 Indications & Dosing – Ondansetron (verify in BNF/datasheet)

• 💧 IV should be given over at least 2–5 min to reduce arrhythmia risk.

🔄 Interactions

• See BNF – avoid with other QT-prolonging drugs (e.g. amiodarone, macrolides, antipsychotics).
• ⚡ May increase risk of serotonin syndrome when combined with SSRIs, SNRIs, MAOIs, or other serotonergic agents.

⚠️ Cautions

• 💔 QT prolongation risk – caution in those with arrhythmias, electrolyte imbalance, or on other QT-prolonging meds.
• 📉 Severe hepatic impairment – max dose 8 mg daily.
• 👶 Neonates/infants – use with caution (immature hepatic metabolism).

🚫 Contraindications

• Hypersensitivity to ondansetron or other 5-HT₃ antagonists.
• Concomitant use with apomorphine (severe hypotension and loss of consciousness reported).
• Bowel obstruction

💥 Side Effects

• 🤢 Constipation (common).
• 🧠 Headache, dizziness.
• 🌡️ Flushing, hiccups.
• 💔 QT prolongation, arrhythmias (rare but serious).
• ⚡ Rare: serotonin syndrome (with serotonergic drugs), seizures, anaphylaxis.
• 🫁 Rare: transient visual disturbances during IV administration.

📑 References

• BNF: Ondansetron
• MHRA Drug Safety Update: Ondansetron & QT prolongation