Ondansetron Accord (Ondansetron)

Ondansetron is an antiemetic that acts on the serotonin pathway to control nausea and vomiting.

• Chemotherapy‑induced nausea and vomiting: reduces the frequency and severity of nausea and vomiting associated with cancer chemotherapy.
• Radiotherapy‑induced nausea and vomiting: helps control nausea and vomiting that occur during or after radiation treatment.
• Postoperative nausea and vomiting: prevents and treats nausea and vomiting following surgical procedures.

• Ondansetron selectively blocks serotonin 5‑HT3 receptors located in the chemoreceptor trigger zone of the central nervous system and on vagal afferents in the gastrointestinal tract. By inhibiting the action of serotonin at these sites, it prevents the initiation of the vomiting reflex triggered by chemotherapeutic agents, radiation, or surgical stimuli.

Common side effects are generally mild and transient.

Common Side Effects

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

Serious or Rare Side Effects

• QT interval prolongation: may predispose to cardiac arrhythmias.
• Severe allergic reaction (anaphylaxis): rash, swelling, difficulty breathing.
• Serotonin syndrome: agitation, hyperthermia, muscle rigidity when combined with other serotonergic drugs.
• Cardiac arrhythmia: irregular heartbeat.
• Hypotension: sudden drop in blood pressure.

Before initiating therapy, consider patient‑specific factors and monitor appropriately.

• Cardiac assessment: evaluate history of arrhythmias or prolonged QT interval.
• Electrolyte monitoring: correct hypokalaemia or hypomagnesaemia which can exacerbate QT prolongation.
• Hepatic impairment: use with caution in patients with severe liver disease.
• Hypersensitivity: avoid in individuals with known allergy to ondansetron or formulation components.
• Renal impairment: dose adjustment may be required in severe renal dysfunction.
• Store at ambient temperature: keep in original packaging, protect from moisture and light.

Ondansetron may interact with other medications that affect serotonin pathways or cardiac conduction.

Major Interactions (Avoid)

• Apomorphine: concurrent use can cause severe hypotension and loss of consciousness.
• Other serotonergic agents (e.g., SSRIs, MAO inhibitors): increased risk of serotonin syndrome.
• Drugs that prolong QT interval (e.g., certain antiarrhythmics): additive risk of cardiac arrhythmias.

Moderate Interactions (Monitor Closely)

• Carbamazepine: may reduce ondansetron plasma concentrations, decreasing efficacy.
• Erythromycin or other macrolide antibiotics: may increase ondansetron levels, requiring monitoring for side effects.