Requires Prescription: Yes

Generics: Ondansetron

Used For: Nausea & Vomiting

How It Works:

Ondansetron is a selective antagonist of the 5-HT3 serotonin receptor subtype. Its precise mechanism in preventing nausea and vomiting associated with chemotherapy is not fully understood. It is believed to act by blocking serotonin receptors involved in initiating the vomiting reflex. This reflex is triggered by serotonin released from enterochromaffin cells in the small intestine during chemotherapy or radiotherapy. Ondansetron may inhibit this reflex by antagonizing 5-HT3 receptors on vagal afferents. It may also influence serotonin release in the central nervous system, though its exact role in postoperative nausea and vomiting is not clearly 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 its components. It should not be used with apomorphine due to the risk of profound hypotension and loss of consciousness.

Precautions:

Use with caution in patients who have shown hypersensitivity to other 5-HT3 receptor antagonists, as they may experience similar hypersensitivity reactions.

Warnings:

Ondansetron can prolong the QT interval in a dose-dependent manner. Avoid use in patients with congenital long QT syndrome. ECG monitoring is advised for patients with electrolyte imbalances (e.g., hypokalemia, hypomagnesemia), congestive heart failure, bradyarrhythmias, or those on other QT-prolonging medications.

Ondansetron may obscure 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 replace 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