Granisetron: Uses, Dosage & Side Effects
Granisetron is an antiemetic drug that prevents nausea and vomiting, especially caused by chemotherapy and radiotherapy. It belongs to the class of 5-HT3 receptor antagonists.
Things worth knowing about "Granisetron"
Granisetron is an antiemetic drug that prevents nausea and vomiting, especially caused by chemotherapy and radiotherapy. It belongs to the class of 5-HT3 receptor antagonists.
What is Granisetron?
Granisetron is an antiemetic medication (a drug used to prevent nausea and vomiting) belonging to the class of 5-HT3 receptor antagonists. It was developed to prevent nausea and vomiting triggered by chemotherapy, radiotherapy, or surgical procedures. The active substance is available in several formulations, including tablets, injectable solutions, and transdermal patches.
Mechanism of Action
Granisetron works by selectively blocking serotonin receptors of the 5-HT3 subtype, which are found both in the central nervous system and in the gastrointestinal tract. During chemotherapy or radiotherapy, large amounts of serotonin (5-hydroxytryptamine) are released in the gut. This serotonin activates the vomiting center in the brain via the vagus nerve, triggering nausea and vomiting. By blocking these receptors, granisetron interrupts this signal pathway and effectively prevents the onset of nausea.
Indications
- Chemotherapy-induced nausea and vomiting (CINV): Granisetron is commonly used prophylactically before and after chemotherapy, particularly with highly emetogenic chemotherapy regimens.
- Radiotherapy-induced nausea and vomiting (RINV): It is also used to prevent nausea and vomiting associated with abdominal or total body irradiation.
- Postoperative nausea and vomiting (PONV): Granisetron may be administered to prevent or treat nausea following surgical procedures.
Dosage and Forms
The dosage of granisetron depends on the indication and the formulation used:
- Oral (tablets): Typically 1 mg to 2 mg administered before chemotherapy, with additional doses as needed.
- Intravenous (injection/infusion): Usually 10 µg/kg body weight, given shortly before chemotherapy.
- Transdermal patch: The patch releases the active substance continuously over several days and is applied before the start of chemotherapy. It is especially suitable for patients who have difficulty swallowing or cannot tolerate oral medications.
The exact dosage should always be determined by the treating physician.
Side Effects
Granisetron is generally well tolerated. Possible side effects may include:
- Common: Headache, constipation, fatigue, elevated liver enzyme levels.
- Occasional: Diarrhea, dizziness, insomnia.
- Rare: Hypersensitivity reactions (allergic reactions), QT prolongation (a change in the heart rhythm visible on an ECG).
Patients with known cardiac arrhythmias or a history of QT prolongation should inform their physician before starting treatment with granisetron.
Drug Interactions
Granisetron may interact with other medications, particularly:
- Other drugs that prolong the QT interval (e.g., certain antibiotics, antiarrhythmic agents).
- Serotonergic substances (e.g., SSRIs, SNRIs, triptans): In rare cases, a serotonin syndrome may occur -- a potentially life-threatening condition caused by excess serotonin activity in the body.
- Apomorphine: Concurrent use is contraindicated due to the risk of a severe drop in blood pressure.
Contraindications
Granisetron should not be used in cases of:
- Known hypersensitivity to the active substance or any of the excipients.
- Concomitant use of apomorphine.
- Severe hepatic impairment (use with caution).
Granisetron During Pregnancy and Breastfeeding
The safety of granisetron during pregnancy and breastfeeding has not been fully established. It should only be used after careful assessment of the benefits versus risks by the treating physician. Animal studies have not shown direct harmful effects on the unborn child, but human data remain limited.
References
- European Medicines Agency (EMA): Granisetron - Summary of Product Characteristics. Available at: www.ema.europa.eu
- Hesketh PJ et al. - Antiemetics: ASCO Guideline Update. Journal of Clinical Oncology, 2020; 38(24): 2782-2797.
- Brunton LL, Hilal-Dandan R, Knollmann BC (eds.) - Goodman & Gilman's The Pharmacological Basis of Therapeutics. 13th edition. McGraw-Hill Education, 2018.
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