Ondansetron Kabi (Ondansetron Hydrochloride Dihydrate)

Ondansetron is a selective 5‑HT3 receptor antagonist used to control nausea and vomiting in several clinical settings.

• Chemotherapy‑induced nausea and vomiting: reduces the incidence and severity of both acute and delayed episodes.
• Radiotherapy‑induced nausea and vomiting: helps prevent nausea associated with radiation treatment.
• Postoperative nausea and vomiting: used to prevent nausea and vomiting after surgical procedures.

• Ondansetron selectively blocks peripheral and central 5‑HT3 receptors located on vagal nerve terminals and in the chemoreceptor trigger zone. By antagonizing serotonin binding, it inhibits the reflex pathway that mediates nausea and vomiting, thereby preventing the initiation of the emetic response triggered by chemotherapeutic agents, radiation, or surgical stimuli. The blockade is rapid, reversible, and dose‑dependent, providing effective control of emesis without affecting other serotonin receptor subtypes.

Ondansetron may cause adverse reactions, which are categorized by frequency and severity.

Common Side Effects

• Headache: mild to moderate intensity.
• Constipation: reduced bowel movements.
• Dizziness: transient light‑headedness.
• Injection site reactions: erythema or mild pain.
• Fatigue: feeling of tiredness.
• Diarrhoea: loose stools.

Serious or Rare Side Effects

• QT prolongation: potential cardiac arrhythmia.
• Severe allergic reactions: anaphylaxis or angioedema.
• Serotonin syndrome: agitation, hyperthermia, tremor.
• Cardiac arrhythmia: ventricular tachycardia.
• Severe hypotension: sudden drop in blood pressure.

When using Ondansetron, consider the following precautions.

• Assess cardiac history: evaluate risk of QT prolongation before use.
• Monitor electrolytes: correct hypokalemia or hypomagnesemia which can predispose to arrhythmia.
• Avoid concomitant use with other QT‑prolonging drugs: review patient medication list.
• Use with caution in hepatic impairment: dose adjustment may be required.
• Pregnancy and lactation: benefit‑risk assessment should be performed as safety data are limited.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Ondansetron can interact with other medicines; interactions are grouped by clinical significance.

Major Interactions (Avoid)

• Concurrent use with other QT‑prolonging agents (e.g., quinidine, haloperidol) may increase risk of cardiac arrhythmia.
• Co‑administration with apomorphine can cause severe hypotension and loss of consciousness.
• Combination with other 5‑HT3 antagonists provides no additional benefit and may increase toxicity.

Moderate Interactions (Monitor Closely)

• CYP3A4 inhibitors (e.g., ketoconazole) may raise ondansetron plasma levels.
• CYP3A4 inducers (e.g., rifampin) may reduce efficacy.
• Serotonergic agents (e.g., SSRIs) may increase risk of serotonin syndrome, requiring monitoring.