Granisetron is a potent, highly selective serotonin 5-HT3 receptor antagonist used primarily for the prevention and treatment of chemotherapy-induced nausea and vomiting (CINV) and postoperative nausea and vomiting (PONV). The 1mg/5ml oral solution formulation offers a convenient alternative for patients who have difficulty swallowing tablets, particularly in pediatric and geriatric populations. It is a cornerstone of antiemetic therapy in oncology protocols.
Adult: Chemotherapy-induced: 1mg to 2mg (5ml to 10ml of 1mg/5ml solution) orally once daily, given up to 1 hour before chemotherapy. A second dose may be given 12 hours after the first for some high-emetogenic regimens. Radiotherapy-induced: 2mg (10ml) once daily given within 1 hour of radiotherapy. Postoperative: 1mg (5ml) to 2mg (10ml) given within 1 hour before induction of anesthesia.
Note: The oral solution can be taken with or without food. Use the measuring cup or oral syringe provided for accurate dosing. Do not use a household spoon. The solution can be diluted in water or apple juice immediately before administration to improve palatability. Do not mix with carbonated drinks or other juices unless stability data confirms compatibility.
Granisetron selectively and competitively blocks serotonin (5-hydroxytryptamine or 5-HT) at the 5-HT3 receptor sites, both peripherally on vagal nerve terminals in the gastrointestinal tract and centrally in the chemoreceptor trigger zone (CTZ) of the area postrema in the medulla oblongata.
Pregnancy: Category B: Animal studies have shown no risk, but no adequate and well-controlled studies in pregnant women. Use only if clearly needed, weighing potential benefits against risks. Often used for hyperemesis gravidarum under specialist care.
Driving: May cause dizziness, drowsiness, or blurred vision. Patients should be cautioned about operating machinery or driving until they are certain granisetron does not affect them adversely.
| Apomorphine | Concomitant use is contraindicated. Severe hypotension and loss of consciousness can occur. | Major |
| Drugs that Prolong QT Interval (e.g., Class IA/III antiarrhythmics, certain antibiotics, antipsychotics) | Additive risk of QT prolongation and cardiac arrhythmias. Monitor ECG. | Major |
| Potent CYP3A4 Inducers (e.g., Rifampicin, Phenytoin, Carbamazepine, St. John's Wort) | May decrease granisetron plasma concentrations, potentially reducing efficacy. | Moderate |
| Other Serotonergic Drugs (e.g., SSRIs, SNRIs, tramadol, fentanyl, lithium) | Theoretical increased risk of serotonin syndrome. Monitor for symptoms. | Moderate |