Ondansetron Ab (Ondansetron)

Ondansetron is a selective serotonin 5‑HT3 receptor antagonist used in the management of nausea and vomiting across several clinical pathways.

• Chemotherapy‑induced nausea and vomiting (CINV): helps control acute and delayed episodes.
• Radiation‑induced nausea and vomiting (RINV): reduces the frequency and severity of symptoms.
• Post‑operative nausea and vomiting (PONV): decreases incidence after general anesthesia.
• Hyper‑emesis gravidarum: provides symptomatic relief when other therapies are insufficient.

• Ondansetron blocks the binding of serotonin to 5‑HT3 receptors located on vagal afferent nerves in the gastrointestinal tract and the chemoreceptor trigger zone of the brain. By inhibiting this receptor, it prevents the neural signaling that initiates the vomiting reflex, thereby reducing nausea and vomiting associated with chemotherapy, radiation, and surgery.

Adverse reactions to ondansetron are generally mild to moderate, but clinicians monitor both common and rare events.

Common Side Effects

• Headache: mild to moderate intensity.
• Constipation: occasional bowel habit changes.
• Diarrhoea: transient episodes.
• Fatigue: general tiredness.
• Dizziness: brief sensations of light‑headedness.

Serious or Rare Side Effects

• QT interval prolongation: may predispose to cardiac arrhythmias.
• Severe allergic reaction: rash, itching, swelling, or anaphylaxis.
• Serotonin syndrome: rare when combined with other serotonergic agents.
• Hepatic enzyme elevation: abnormal liver function tests.
• Vision changes: blurred vision or visual disturbances.

When prescribing ondansetron, clinicians consider several safety factors to minimise risk.

• Cardiac monitoring: assess baseline ECG in patients with known QT prolongation risk.
• Electrolyte balance: correct hypokalaemia, hypomagnesemia, or hypocalcaemia before use.
• Drug interactions: review concomitant medications that may affect cardiac rhythm.
• Pregnancy: use only if the potential benefit outweighs risk; data are limited.
• Lactation: assess infant exposure risk before breastfeeding.
• Store at below 25°C: keep in the original container, protect from moisture and direct sunlight.

Ondansetron may interact with several drug classes, requiring vigilance from prescribers.

Major Interactions (Avoid)

• Anti‑arrhythmic agents (e.g., amiodarone, quinidine): increase risk of QT prolongation.
• Certain antipsychotics (pharmacologic ).

Moderate Interaction ( "). - "). - "). - "). - "). - ". - "