Ondansetron Kalceks (Ondansetron)

Ondansetron is a 5‑HT3 receptor antagonist used to control nausea and vomiting across several treatment pathways.

• Chemotherapy‑induced nausea and vomiting: prevents and reduces episodes in patients receiving cytotoxic therapy.
• Postoperative nausea and vomiting: reduces the incidence of nausea and vomiting after surgical procedures.
• Radiotherapy‑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 on vagal afferents in the gastrointestinal tract. By inhibiting serotonin binding, it prevents the initiation of the vomiting reflex triggered by chemotherapeutic agents, radiation, or surgical stimuli.

Ondansetron may cause a range of adverse reactions, most of which are mild and transient.

Common Side Effects

• Headache: mild to moderate pain often resolves without intervention.
• Constipation: reduced bowel movements that may require dietary adjustment.
• Dizziness: transient sensation of light‑headedness.
• Fatigue: feeling unusually tired.
• Diarrhea: occasional loose stools.
• Injection site reactions: pain or erythema at the administration site.

Serious or Rare Side Effects

• QT interval prolongation: may lead to cardiac arrhythmias, especially in patients with electrolyte disturbances.
• Severe allergic reactions: including anaphylaxis, rash, or angioedema.
• Serotonin syndrome: rare but possible when combined with other serotonergic agents.
• Hepatic dysfunction: elevated liver enzymes in susceptible individuals.
• Severe hypotension: sudden drop in blood pressure after rapid IV administration.
• Neuroleptic malignant syndrome: extremely rare neurological emergency.

Before using Ondansetron, clinicians should consider several safety measures.

• Cardiac risk assessment: evaluate baseline ECG and electrolyte status to mitigate QT prolongation.
• Hepatic impairment: adjust use in patients with significant liver disease.
• Renal impairment: monitor dosing in severe renal dysfunction.
• Hypersensitivity: avoid in individuals with known allergy to ondansetron or formulation components.
• Concomitant serotonergic drugs: use caution to prevent serotonin syndrome.
• Store at ambient temperature: keep in original packaging, protect from moisture and light.

Ondansetron can interact with other medicines, requiring attention to avoid adverse outcomes.

Major Interactions (Avoid)

• Apomorphine: concurrent use may cause profound hypotension and loss of consciousness.
• Other QT‑prolonging agents (e.g., quinidine, haloperidol): increase risk of cardiac arrhythmias.
• Serotonergic agents (e.g., SSRIs, MAO inhibitors): may precipitate serotonin syndrome.

Moderate Interactions (Monitor Closely)

• Carbamazepine: induces metabolism, potentially reducing ondansetron efficacy.
• Dexamethasone: may enhance anti‑emetic effect, requiring dose adjustment.
• Anesthetic agents (e.g., propofol): may increase risk of hypotension.
• Rifampin: may lower plasma concentrations of ondansetron.