Ondansetron Noridem (Ondansetron)

• Ondansetron is a selective 5‑HT3 receptor antagonist used to control nausea and vomiting in several clinical situations.
• Chemotherapy‑induced nausea and vomiting: reduces the incidence and severity of nausea and vomiting in patients receiving cytotoxic chemotherapy.
• Postoperative nausea and vomiting: prevents nausea and vomiting after surgical procedures.
• Radiation therapy‑induced nausea and vomiting: helps control nausea associated with radiation treatment.

• Ondansetron selectively blocks serotonin 5‑HT3 receptors located in the chemoreceptor trigger zone of the brain and in the gastrointestinal tract. By inhibiting serotonin binding, it interrupts the neural pathways that trigger the vomiting reflex, thereby reducing nausea and emesis associated with chemotherapy, radiation, and surgery.

Common Side Effects

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

Serious or Rare Side Effects

• QT interval prolongation: may lead to cardiac arrhythmias.
• Severe allergic reaction (anaphylaxis): difficulty breathing, rash, swelling.
• Serotonin syndrome: agitation, hyperthermia, muscle rigidity.
• Cardiac arrhythmia: irregular heart rhythm requiring medical attention.
• Hypotension: sudden drop in blood pressure.
• Hepatic dysfunction: abnormal liver enzyme elevations.

• Before initiating therapy, consider the following safety measures.
• Assess cardiac risk: evaluate QT interval and correct electrolyte imbalances.
• Monitor electrolytes: treat hypokalaemia or hypomagnesemia before use.
• Use with caution in hepatic impairment: dose adjustment may be required.
• Avoid in patients with known hypersensitivity to ondansetron or other 5‑HT3 antagonists.
• Pregnancy and lactation: use only if the potential benefit justifies the potential risk.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Ondansetron may interact with several drug classes; review patient medication lists.

Major Interactions (Avoid)

• Apomorphine: concurrent use can cause profound hypotension and loss of consciousness.
• Other QT‑prolonging agents: increased risk of cardiac arrhythmia.
• Serotonergic agents (e.g., SSRIs, MAO inhibitors): potential for serotonin syndrome.

Moderate Interactions (Monitor Closely)

• CYP3A4 inhibitors (e.g., ketoconazole): may increase ondansetron plasma concentrations.
• CYP2D6 inhibitors (e.g., fluoxetine): may modestly raise exposure levels.
• Alcohol: may enhance central nervous system effects such as dizziness.