Onaseron 8

Indications

Onaseron is a serotonin 5-HT3 receptor antagonist indicated for:

• Prevention of nausea and vomiting related to both initial and repeated courses of emetogenic cancer chemotherapy.
• Prevention and management of post-operative nausea and vomiting.
• Prevention of nausea and vomiting caused by radiotherapy.

Always follow the advice of a registered healthcare professional before taking medication.

Description

Onaseron is an orally dissolving film that is placed on the tongue, dissolving within approximately 20 seconds for easy swallowing without the need for water. The active ingredient, Onaseron base, acts as a selective blocker of serotonin 5-HT3 receptors, with a molecular formula of C18H19N3O and a molecular weight of 293.3.

Pharmacology

Onaseron functions as a powerful 5-HT3 receptor antagonist. While its exact mechanism for controlling nausea and vomiting is not fully understood, it is believed that chemotherapeutic agents and radiotherapy may trigger the release of serotonin (5-HT) in the small intestine, activating a vomiting reflex through vagal afferents via 5-HT3 receptors. Onaseron blocks this reflex initiation. Additionally, activation of these receptors may lead to serotonin release in the central nervous system, contributing to nausea. Thus, Onaseron’s effectiveness in managing nausea and vomiting due to chemotherapy and radiotherapy likely stems from its action on both peripheral and central 5-HT3 receptors.

Dosage

For Chemotherapy-Induced Nausea and Vomiting:

• Adults & Pediatric Patients (6 months to 18 years):
  • 8 mg tablet/orodispersible tablet: Administer three doses of 0.15 mg/kg, not exceeding 16 mg per dose.
  • 4 mg orodispersible tablet: Same dosing as above.
  • Injection: Three doses of 0.15 mg/kg, up to 16 mg per dose, infused intravenously over 15 minutes.

For Radiotherapy-Induced Nausea and Vomiting:

• Adults:
  • 8 mg tablet/orodispersible tablet: Start with 8 mg orally 1-2 hours before radiotherapy, followed by 8 mg every 8 hours for up to 5 days post-treatment.

For Postoperative Nausea and Vomiting:

• Adults:
  • 8 mg tablet/orodispersible tablet: Administer 16 mg as two 8 mg tablets.
  • 4 mg orodispersible tablet: Same as above.
  • Injection: 4 mg.

For Pediatric Patients (>40 kg):

• Injection: 4 mg.

Oral Solutions:

• Radiotherapy Induced Nausea and Vomiting: Recommended dosage is 10 ml (8 mg) three times daily, with specific instructions based on the type of radiotherapy.

Administration Instructions for Oral Soluble Film

1. Open the pouch carefully along the tear mark.
2. Place the film on your tongue; it will dissolve in about 20 seconds.
3. Avoid chewing or swallowing the film whole.
4. Swallow the dissolved film, with or without liquid.
5. Wash your hands after handling the film.

Always follow the advice of a registered healthcare professional before taking medication.

Interactions

Onaseron does not appear to affect the cytochrome P-450 enzyme system in the liver. However, since it is metabolized by these enzymes, medications that induce or inhibit them may alter Onaseron’s clearance and half-life. No dosage adjustments are typically needed for patients taking these medications.

Contraindications

Onaseron is contraindicated in patients with known hypersensitivity to the drug or its components, and in those using apomorphine concurrently.

Side Effects

Common side effects include headache, constipation, and diarrhea, generally mild to moderate. Rarely, patients may experience rash, flushing, hiccups, or liver enzyme abnormalities. Anaphylaxis and bronchospasm have been reported, although their relationship to Onaseron is not clearly established. There is no evidence linking Onaseron to extrapyramidal reactions.

Pregnancy & Lactation

Long-term studies have shown no carcinogenic effects in rats and mice at doses up to 30 mg/kg per day. No significant reproductive harm was noted in animal studies. However, adequate studies in pregnant women are lacking, and caution is advised when administering Onaseron to nursing mothers.

Precautions & Warnings

Hypersensitivity reactions may occur in patients with prior reactions to other 5-HT3 receptor antagonists. Onaseron should not replace nasogastric suction and may mask signs of progressive ileus or gastric distension after abdominal surgery or in patients with chemotherapy-induced nausea.

Use in Special Populations

• Renal Impairment: No dosage adjustment needed.
• Hepatic Impairment: For severe cases, a maximum daily dose of 8 mg is recommended, infused over 15 minutes before chemotherapy.
• Pediatric Patients (under 4 years): Limited information is available.
• Geriatric Patients (over 65): No dosage adjustment is required.

Storage Conditions

Store in a dry place at temperatures not exceeding 30ºC. Protect from light and moisture.