Kytril (Granisetron)

Kytril (granisetron) is a 5‑HT3 receptor antagonist used to control nausea and vomiting associated with chemotherapy and surgery.

• Chemotherapy‑induced nausea and vomiting: reduces frequency and severity of acute and delayed episodes in patients receiving cytotoxic agents.
• Postoperative nausea and vomiting: prevents nausea and vomiting after general anesthesia and surgical procedures.
• Radiation‑induced nausea and vomiting: mitigates nausea in patients undergoing radiotherapy.

• Granisetron selectively blocks serotonin (5‑HT3) receptors located on vagal afferents in the gastrointestinal tract and in the chemoreceptor trigger zone of the brain. By preventing serotonin from binding, it interrupts the emetic signaling cascade that is triggered by chemotherapy agents or surgical stimuli, thereby reducing the initiation of nausea and vomiting reflexes.

Common Side Effects

• Headache: mild to moderate pain in the head region.
• Constipation: reduced bowel movements, may require laxatives.
• Dizziness: sensation of light‑headedness or unsteadiness.
• Fatigue: feeling of tiredness or reduced energy.
• Diarrhea: loose stools occurring intermittently.
• Injection site reaction: redness, swelling or pain at the infusion site.

Serious or Rare Side Effects

• Anaphylactic reaction: potentially life‑threatening hypersensitivity requiring immediate medical attention.
• Cardiac arrhythmia (including QT prolongation): may cause serious rhythm disturbances.
• Severe constipation or intestinal obstruction: requires prompt evaluation.
• Seizures: rare neurologic event that necessitates urgent care.

Before administering Kytril, consider the following precautions:

• Renal impairment: monitor renal function as the drug is excreted unchanged.
• Hepatic impairment: use with caution in patients with liver disease.
• Cardiac risk: avoid in patients with known QT prolongation or other arrhythmias.
• Pregnancy: prescribe only if the potential benefit justifies the potential risk to the fetus.
• Drug interactions: review concomitant medications that may affect cardiac conduction or granisetron levels.
• Store at 2‑8 °C: keep refrigerated, protect from light, do not freeze or shake.

Granisetron may interact with other medicines as follows:

Major Interactions (Avoid)

• Other QT‑prolonging agents: increased risk of serious cardiac arrhythmia.
• Concomitant use of other 5‑HT3 antagonists: additive antiemetic effect not recommended.
• Strong CYP3A4 inhibitors (e.g., ketoconazole): may raise granisetron plasma concentrations.
• Strong CYP3A4 inducers (e.g., rifampicin): may reduce granisetron efficacy.

Moderate Interactions (Monitor Closely)

• Anticholinergic agents: may exacerbate constipation.
• Opioids: may enhance sedation and respiratory depression.
• Diuretics: may alter electrolyte balance, affecting cardiac safety.