Requires Prescription: Yes
Generics: Ondansetron
Used For: Nausea & Vomiting
How It Works:
Ondansetron is a selective antagonist of the 5-HT3 serotonin receptor subtype. While its exact mechanism in preventing chemotherapy-induced nausea and vomiting is not fully understood, it is believed to work by blocking serotonin receptors involved in the vomiting reflex. This reflex is triggered by the release of serotonin from the small intestine during chemotherapy or radiotherapy, which stimulates 5-HT3 receptors on vagal afferents. Ondansetron may inhibit this reflex by antagonizing these receptors. It may also influence serotonin release in the central nervous system, though its exact role in postoperative nausea and vomiting is not well defined.
Dosage: Follow specific dosing instructions provided 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:
For the 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. It should not be used concurrently with apomorphine due to the risk of profound hypotension and loss of consciousness.
Precautions:
Be cautious in patients who have exhibited hypersensitivity to other 5-HT3 receptor antagonists, as they may experience hypersensitivity reactions such as anaphylaxis or bronchospasm.
Warnings:
Ondansetron may 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 this medication during pregnancy.
Storage: Store at room temperature, away from direct light and heat.
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