Ondansetron Kalceks (Ondansetron)

Ondansetron is a selective 5‑HT3 receptor antagonist used to control nausea and vomiting in several clinical settings.

• Chemotherapy‑induced nausea and vomiting: prevents and reduces acute and delayed episodes in cancer patients receiving cytotoxic agents.
• Postoperative nausea and vomiting: administered before or after surgery to lower the incidence of vomiting and the need for rescue medication.
• Radiotherapy‑induced nausea and vomiting: helps manage nausea in patients undergoing radiation treatment, improving comfort and treatment adherence.

• 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 cascade triggered by chemotherapeutic agents, radiation, or surgical stimuli, thereby reducing nausea and vomiting.

Ondansetron is generally well tolerated, but adverse reactions can occur.

Common Side Effects

• Headache: mild to moderate pain often resolves without intervention.
• Constipation: reduced bowel movements, may be managed with diet or laxatives.
• Dizziness: transient sensation of light‑headedness.
• Fatigue: feeling unusually tired or weak.
• Diarrhea: loose stools occurring shortly after administration.

Serious or Rare Side Effects

• Cardiac arrhythmia: irregular heart rhythm, especially with rapid intravenous infusion.
• Severe allergic reaction: rash, itching, swelling, or anaphylaxis requiring immediate medical attention.
• Serotonin syndrome: rare but potentially life‑threatening condition when combined with other serotonergic drugs.
• Elevated liver enzymes: abnormal liver function tests indicating hepatic stress.
• Vision changes: blurred vision or visual disturbances.

Before using Ondansetron, consider the following safety measures.

• Cardiac monitoring: avoid rapid IV administration in patients with known QT prolongation.
• Drug interactions: review concomitant medications that may affect cardiac rhythm or serotonin levels.
• Pregnancy: use only if the potential benefit justifies the potential risk to the fetus.
• Breastfeeding: assess risk versus benefit, as the drug may be excreted in milk.
• Renal/hepatic impairment: dose adjustment may be required based on clinical judgment.
• Store at 2‑8°C: keep refrigerated, protect from light, do not freeze or shake.

Ondansetron may interact with several medications, altering efficacy or safety.

Major Interactions (Avoid)

• Certain antiarrhythmic agents (e.g., amiodarone, quinidine): increase risk of QT prolongation.
• Other serotonergic drugs (e.g., SSRIs, MAO inhibitors): may precipitate serotonin syndrome.
• Apomorphine: can cause severe hypotension and loss of consciousness.

Moderate Interactions (Monitor Closely)

• CYP3A4 inhibitors (e.g., erythromycin, ketoconazole): may raise ondansetron plasma levels.
• CYP2D6 substrates (e.g., codeine, tramadol): potential for altered metabolism.
• Anesthetics (e.g., propofol): may enhance sedative effects.