Ondansetron Hexal (Ondansetron Hydrochloride Dihydrate)

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

• Chemotherapy-induced nausea and vomiting: prevents and treats nausea and vomiting in patients receiving cytotoxic chemotherapy.
• Radiotherapy-induced nausea and vomiting: reduces nausea and vomiting associated with radiation therapy.
• Postoperative nausea and vomiting: helps prevent nausea and vomiting after surgical procedures.

• Ondansetron selectively blocks peripheral and central serotonin (5‑HT3) receptors, inhibiting the transmission of emetic signals from the gastrointestinal tract and the chemoreceptor trigger zone to the vomiting centre in the brain, thereby reducing the incidence of nausea and vomiting.

Ondansetron may cause a range of adverse reactions, varying from mild to serious.

Common Side Effects

• Headache: mild to moderate pain in the head.
• Constipation: reduced bowel movements or hard stools.
• Dizziness: sensation of light‑headedness or unsteadiness.
• Fatigue: feeling unusually tired or weak.
• Diarrhoea: loose, watery stools.
• Injection site reactions: pain, erythema, or swelling at the IV site.

Serious or Rare Side Effects

• QT prolongation: abnormal heart rhythm that may lead to arrhythmia.
• Severe allergic reactions: anaphylaxis, rash, or swelling.
• Serotonin syndrome: potentially life‑threatening condition when combined with other serotonergic agents.
• Cardiac arrhythmias: irregular heartbeats beyond QT changes.
• Severe hypotension: marked drop in blood pressure.

Before initiating therapy, clinicians should consider several safety aspects.

• Assess cardiac risk: monitor QT interval in patients with known cardiac disease or electrolyte imbalance.
• Avoid in patients with known hypersensitivity: do not use if the patient has reacted to ondansetron or other 5‑HT3 antagonists.
• Use caution in hepatic impairment: dose adjustment may be required for reduced liver function.
• Consider pregnancy status: evaluate risk versus benefit as safety data are limited.
• Monitor for serotonin syndrome: watch for signs when combined with serotonergic drugs.
• Store at ambient temperature: keep in original container, protect from light and moisture.

Ondansetron can interact with other medicines, requiring attention to the level of risk.

Major Interactions (Avoid)

• Concurrent use with other QT‑prolonging drugs: may increase risk of cardiac arrhythmia.
• Combination with apomorphine: can cause severe hypotension and loss of consciousness.
• Use with serotonergic agents (e.g., SSRIs, MAOIs): may increase risk of serotonin syndrome.

Moderate Interactions (Monitor Closely)

• CYP3A4 inhibitors (e.g., ketoconazole): may increase ondansetron plasma levels.
• CYP2D6 inhibitors (e.g., fluoxetine): may modestly increase exposure.
• Ritonavir: may raise ondansetron concentrations; monitor for side effects.