Indications
Granisetron is used to prevent and treat nausea and vomiting caused by cancer chemotherapy and radiotherapy, and to prevent and treat nausea and vomiting after surgery. It is available as tablets, as an injection given by a doctor or nurse, and in some countries as a skin patch.
How It Works
Chemotherapy, radiotherapy and surgery can cause cells in the gut to release serotonin (5-HT), which triggers nerve signals to the vomiting centre in the brain. Granisetron blocks the 5-HT3 receptors on these nerves and in the brain, so the signals that cause nausea and vomiting are reduced.
Dosage and Administration
- Tablets (adults, chemotherapy or radiotherapy): commonly 1 mg twice daily or 2 mg once daily, with the first dose given about 1 hour before treatment, for the number of days prescribed.
- Injection: given intravenously by a doctor or nurse before chemotherapy or at the end of surgery, at the dose prescribed.
- Children and other forms: as prescribed.
It is often combined with a corticosteroid such as Dexamethasone and other anti-sickness medicines.
Interactions
- Serotonergic medicines such as SSRIs (Fluoxetine, Sertraline), SNRIs, Tramadol, Fentanyl and Lithium: rare risk of serotonin syndrome.
- Medicines that prolong the QT interval (some antiarrhythmics, antipsychotics, macrolide antibiotics): increased risk of heart rhythm problems.
- Apomorphine: must not be combined with 5-HT3 blockers because of severe low blood pressure.
Contraindications
- Allergy to Granisetron or other 5-HT3 receptor blockers such as Ondansetron.
Side Effects
Common side effects include constipation, headache, tiredness, dizziness and, occasionally, diarrhoea and sleep problems. Less common effects include changes in liver tests, rash and changes in heart rhythm (QT prolongation).
Get urgent medical help if you have a fast or irregular heartbeat, fainting, signs of serotonin syndrome (agitation, confusion, fever, sweating, shaking, muscle twitching), severe constipation with abdominal pain and swelling, or swelling of the face or throat with difficulty breathing.
Pregnancy and Lactation
Avoid during pregnancy unless the doctor decides it is needed, as experience is limited. It is not known whether it passes into breast milk; breastfeeding is usually not recommended during treatment.
Precautions and Warnings
- Tell your doctor if you have heart rhythm problems or low potassium or magnesium.
- It may hide signs of a bowel blockage; report severe constipation or abdominal swelling.
- Use with care in liver disease.
Overdose
Overdose may cause headache and possible heart rhythm changes. There is no specific antidote; seek medical help for monitoring and supportive care.
Therapeutic Class
Antiemetic: 5-HT3 receptor antagonist.
Storage
Tablets: store below 30°C in a dry place, away from light and out of the reach of children. Injections: as directed on the pack; do not freeze.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.