Requires Prescription: Yes
Generics: Ondansetron
Used For: Nausea & Vomiting
How it Works:
Ondansetron is a selective antagonist of the 5-HT3 serotonin receptor subtype. It is used to prevent nausea and vomiting, especially in chemotherapy settings. While the exact mechanism is not fully understood, ondansetron is believed to block serotonin receptors that initiate the vomiting reflex. This reflex is triggered by the release of serotonin from the small intestine in response to chemotherapy or radiotherapy. Ondansetron’s antiemetic effects may stem from blocking these receptors in both the peripheral and central nervous systems. The precise action of ondansetron in postoperative nausea and vomiting remains unclear.
Dosage: Follow the specific dosing instructions for ondansetron.
Side Effects:
Chemotherapy-Induced Nausea and Vomiting: Diarrhea, headache, fever, constipation, rash. Rarely: angina, ECG changes, hypotension, tachycardia, QT prolongation, ST segment depression, bradycardia, transient liver enzyme elevations, neurological effects such as seizures or extrapyramidal reactions, and hypokalemia.
Postoperative Nausea and Vomiting: Headache, drowsiness/sedation, injection site reactions, fever, cold sensation, pruritus, paresthesia. Rarely: pain, redness, burning at the injection site, hiccups, urticaria, Stevens-Johnson syndrome, toxic epidermal necrolysis, transient blindness, oculogyric crisis, and dizziness.
Drug Interactions:
Cytochrome P-450 Enzyme Modifiers: Apomorphine, phenytoin, carbamazepine, rifampin.
Serotonergic Drugs: Tramadol.
Chemotherapy Agents: Carmustine, etoposide, cisplatin.
Others: Temazepam, alfentanil, atracurium.
Indication:
Prevention of nausea and vomiting associated with initial and repeat courses of emetogenic cancer chemotherapy.
When Not to Use:
Ondansetron is contraindicated in patients with known hypersensitivity to the drug or any of its components. Concurrent use with apomorphine is contraindicated due to the risk of profound hypotension and loss of consciousness.
Precautions:
Hypersensitivity reactions, including anaphylaxis and bronchospasm, have been reported in patients sensitive to other 5-HT3 receptor antagonists.
Warnings:
Ondansetron can prolong the QT interval in a dose-dependent manner. It should be avoided in patients with congenital long QT syndrome. ECG monitoring is recommended for patients with electrolyte imbalances (e.g., hypokalemia, hypomagnesemia), heart failure, bradyarrhythmias, or those on other QT-prolonging medications.
Ondansetron may mask symptoms of progressive ileus and gastric distention in patients undergoing abdominal surgery or experiencing chemotherapy-induced nausea and vomiting.
Ondansetron does not stimulate gastric or intestinal peristalsis and should not be used as a substitute for nasogastric suction.
Additional Information:
Pregnancy Category: Consult your physician before using any medication during pregnancy.
Storage: Store at room temperature, away from direct light and heat.
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