Ondansetron Accord-Uk (Ondansetron)

Ondansetron is a 5‑HT3 receptor antagonist that prevents nausea and vomiting caused by specific medical treatments.

• Chemotherapy‑induced nausea and vomiting: reduces incidence and severity in patients receiving cytotoxic chemotherapy.
• Postoperative nausea and vomiting: helps prevent nausea and vomiting after surgical procedures.
• Radiotherapy‑induced nausea and vomiting: mitigates nausea and vomiting caused by radiation treatment.

• Ondansetron selectively blocks peripheral and central 5‑HT3 receptors, inhibiting serotonin binding that triggers the vomiting reflex. By antagonizing these receptors in the chemoreceptor trigger zone and gastrointestinal tract, it prevents the initiation of nausea and vomiting pathways without affecting other neurotransmitter systems.

Common Side Effects

• Headache: mild to moderate pain in the head region.
• Constipation: reduced bowel movements, occasional abdominal discomfort.
• Dizziness: transient sensation of light‑headedness.
• Fatigue: feeling unusually tired or weak.
• Injection site reaction: pain, erythema, or swelling at the administration site.
• Diarrhoea: loose stools occurring shortly after dosing.

Serious or Rare Side Effects

• QT interval prolongation: potential cardiac rhythm disturbance.
• Severe allergic reaction (anaphylaxis): hives, swelling, difficulty breathing.
• Serotonin syndrome: agitation, hyperthermia, muscle rigidity when combined with serotonergic agents.
• Cardiac arrhythmia: irregular heartbeats requiring medical attention.
• Severe hypotension: sudden drop in blood pressure.
• Hepatic dysfunction: abnormal liver enzyme elevations.

Before initiating therapy, consider the following precautions:

• Cardiac monitoring: assess QT interval in patients with known cardiac risk factors.
• Electrolyte balance: correct hypokalaemia or hypomagnesaemia prior to use.
• Drug interactions: review concomitant medications that may prolong QT interval.
• Pregnancy: use only if the potential benefit justifies the potential risk to the fetus.
• Renal/hepatic impairment: dose adjustment may be required; monitor organ function.
• Store at ambient temperature: keep below 25°C, protect from moisture and light, retain in original packaging.

Ondansetron may interact with several drug classes:

Major Interactions (Avoid)

• QT‑prolonging agents (e.g., amiodarone, quinidine, cisapride): increase risk of cardiac arrhythmias.
• Apomorphine: may cause severe hypotension.
• Carbamazepine: induces metabolism, reducing ondansetron efficacy.
• Ritonavir: inhibits metabolism, raising ondansetron plasma levels.

Moderate Interactions (Monitor Closely)

• Dexamethasone: may enhance anti‑emetic effect, requiring dose review.
• Other serotonergic agents: risk of serotonin syndrome, monitor for symptoms.
• Warfarin: possible alteration of INR, monitor coagulation parameters.