Generic

Indications

Ondansetron is a 5-HT3 serotonin receptor antagonist that is used to treat:

• The prevention of nausea and vomiting caused by emetogenic cancer treatment during the initial and subsequent rounds.
• Post-operative nausea and vomiting prevention and therapy.
• Radiation-induced nausea and vomiting can be avoided.

Pharmacology

Ondansetron is a strong and highly specific antagonist of the 5HT3 receptor. Its exact mechanism of action in the treatment of nausea and vomiting is unknown. By stimulating vagal afferents via 5HT3 receptors, chemotherapeutic drugs and radiotherapy may stimulate the release of 5HT in the small intestine, causing a vomiting reflex. Ondansetron inhibits the onset of this response. Activation of vagal afferents may also result in the release of 5HT in the region postrema, which is located on the fourth ventricle’s floor, promoting emesis through a central mechanism.Ondansetron’s action in the management of nausea and vomiting caused by cytotoxic chemotherapy and radiotherapy is most likely due to antagonism of 5HT3 receptors on peripheral and central nervous system neurons. Although the mechanisms of action in post-operative nausea and vomiting are unknown, there may be parallels with cytotoxic-induced nausea and vomiting.

Dosage & Administration

Chemotherapy-Induced Nausea and Vomiting-

Adults, Pediatric patients (6 months to 18 years):

• 8 mg tablet/orodispersible tablet: Three 0.15 mg/kg doses, up to a maximum of 16 mg per dose.
• 4 mg orodispersible tablet: Three 0.15 mg/kg doses, up to a maximum of 16 mg per dose.
• Injection: Three 0.15 mg/kg doses, up to a maximum of 16 mg per dose, infused intravenously over 15 minutes.

Radiotherapy-Induced Nausea and Vomiting-

Adults:

• 8 mg tablet/orodispersible tablet: Initial Dose: 8 mg orally 1 to 2 hours before radiotherapy. Post Radiotherapy: 8 mg orally every 8 hours for up to 5 days after a course of treatment.
• 4 mg orodispersible tablet: Three 0.15 mg/kg doses, up to a maximum of 16 mg per dose.
• Injection: Three 0.15 mg/kg doses, up to a maximum of 16 mg per dose, infused intravenously over 15 minutes.

Postoperative Nausea and Vomiting-

Adults:

• 8 mg tablet/orodispersible tablet: 16 mg given as two 8 mg tablets
• 4 mg orodispersible tablet: 16 mg
• Injection: 4 mg

Pediatrics (>40 kg): Injection: 4 mg
Pediatrics (40 kg): Injection: 0.1 mg/kg

Interaction

Ondansetron appears to have a low risk of clinically significant drug interactions.

Contraindications

Patients with known hypersensitivity to the drug or any of its components should not take it. Apomorphine is being taken at the same time.

Side Effects

Diarrhea, headache, and fever are the most common adverse reactions in chemotherapy-induced nausea and vomiting (incidence 7%). Headache (incidence 10%) is the most common postoperative nausea and vomiting adverse reaction in adults, while diarrhea is the most common adverse reaction in pediatric patients aged 1 to 24 months (incidence 2 percent ).

Pregnancy & Lactation

Pregnancy Classification B. Ondansetron is excreted by rats in their milk. Ondansetron is not known to be excreted in human milk. Ondansetron should be administered with caution to a nursing woman because many drugs are excreted in human milk.

Precautions & Warnings

With or without known hypersensitivity to other selective 5-HT3 receptor antagonists, hypersensitivity reactions such as anaphylaxis and bronchospasm have been reported. The lengthening of the QT interval is dose-dependent.

Therapeutic Class

Anti-emetic medications

Storage Conditions

Keep the temperature below 30°C and away from light and moisture. Keep out of children’s reach.

Pharmaceutical Name