Description
Ondansetron Pharmacodynamics
Ondansetron is a selective 5-NTz (serotonin) receptor antagonist. Cytostatic chemotherapy drugs and radiotherapy may increase serotonin levels, which by activating vagal afferent fibers containing 5-HTZ receptors, causes the gag reflex.
Ondansetron inhibits the onset of the gag reflex by blockade of 5-NTZ receptors at the neuronal level of both the central and peripheral nervous system. Apparently, this mechanism of action is the basis for prevention and treatment of postoperative vomiting and nausea caused by cytostatic chemotherapy and radiotherapy.
Indications
Prevention and elimination of nausea and vomiting caused by cytostatic chemotherapy and radiotherapy as well as postoperative nausea and vomiting.
Contraindications
Hypersensitivity to any component of the drug, pregnancy and lactation.
Children under 2 years of age (safety and effectiveness has not been studied).
Dosage and administration
- Cytostatic therapy.
The choice of dosing regimen is determined by the emetogenicity of antitumor therapy. - For adults, the daily dose is usually 8-32 mg; the following regimens are recommended:
For moderate emetogenic chemotherapy and pi radiotherapy: 8 mg intravenously slowly or intramuscularly just before therapy; - For highly emetogenic chemotherapy:
– 8 mg intravenous jet slowly just before the start of chemotherapy, followed by two more intravenous injections of 8 mg, each 2 to 4 hours later;
– Continuous 24-hour infusion of the drug at a dose of 24 mg at a rate of 1 mg/hour;-16-32 mg diluted in 50-100 ml of an appropriate infusion solution, as a 15-minute infusion, immediately before the start of chemotherapy.The effectiveness of ondansetron may be increased by a single intravenous injection of a glucocorticoid (e.g., 20 mg of the phosphorus-sodium salt of dexamethasone) before the start of chemotherapy. - Children
In children over 2 years of age, the drug is administered at a dose of 5 mg/m2 of body surface area intravenously, immediately before the start of chemotherapy. - Prevention of postoperative nausea and vomiting
In adults, a single dose of 4 mg is administered intramuscularly or intravenously, slowly at the start of anesthesia. To relieve the resulting nausea and vomiting, an intramuscular or slow intravenous injection of 4 mg of the drug is recommended. Intramuscularly to the same area of the body ondansetron may be administered in a dose not exceeding 4 mg! - In children, to prevent postoperative nausea and vomiting, ondansetron is administered parenterally in a single dose of 0.1 mg/kg (up to 4 mg maximum) as a slow intravenous injection before or after anesthesia.
- For treatment of developed postoperative nausea and vomiting in children, slow intravenous injection of a single dose of the drug 0.1 mg/kg (up to max. 4 mg) is recommended.
- There is insufficient experience with regard to the prevention and treatment of postoperative nausea and vomiting in children under 2 years of age.
- Elderly patients.
No change in dosage is required.
