Home Drug Guide Ondansetron Hydrochloride

Drug Guide

Generic Name

Ondansetron Hydrochloride

Brand Names Zofran, Zofran Preservative Free, Zofran And Dextrose In Plastic Container, Ondansetron Hydrochloride Preservative Free, Ondansetron Hydrochloride And Dextrose In Plastic Container

Classification

Therapeutic: Antiemetic

Pharmacological: Selective 5-HT3 receptor antagonist

FDA Approved Indications

Prevention of nausea and vomiting associated with chemotherapy-induced nausea and vomiting (CINV)
Prevention of radiation-induced nausea and vomiting
Preoperative nausea and vomiting

Mechanism of Action

Ondansetron antagonizes 5-HT3 receptors in the central and peripheral nervous systems, which are involved in vomiting reflex pathways, thereby preventing nausea and vomiting.

Dosage and Administration

Adult: Dose varies; commonly 8 mg orally 30 minutes before chemotherapy, repeated every 8 hours as needed, max dose varies by protocol.

Pediatric: Dose based on weight; typically 8-15 mg orally 30 minutes before chemotherapy or radiotherapy; pediatric doses should be individualized.

Geriatric: Use with caution; start at lower end of dosing range due to increased sensitivity.

Renal Impairment: Adjust dose based on severity of impairment.

Hepatic Impairment: Use with caution; dose adjustment may be necessary.

Pharmacokinetics

Absorption: Rapidly absorbed after oral administration.

Distribution: Widely distributed, crosses the blood-brain barrier.

Metabolism: Primarily metabolized in the liver via CYP3A4, CYP2D6, and CYP1A2.

Excretion: Excreted mainly in urine as metabolites; small amount unchanged in feces.

Half Life: Approximately 3-7 hours.

Contraindications

Known hypersensitivity to ondansetron or any component of the formulation.

Precautions

Use with caution in patients with hepatic impairment.
Monitor for hypersensitivity reactions.
Use cautiously in patients with electrolyte abnormalities, as these may predispose to arrhythmias.

Adverse Reactions - Common

Headache (Common)
Constipation (Common)
Dizziness (Common)

Adverse Reactions - Serious

Serotonin syndrome (rare) (Serious)
QT prolongation and Torsades de Pointes (rare) (Serious)
Anaphylaxis (rare) (Serious)

Drug-Drug Interactions

Apomorphine (contraindicated with ondansetron due to hypotension and loss of consciousness)
QT-prolonging drugs (e.g., certain antipsychotics, methadone, certain antibiotics)

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor for effectiveness of antiemetic; assess for signs of hypersensitivity.

Diagnoses:

Nausea related to chemotherapy.
Risk of electrolyte imbalance due to vomiting.

Implementation: Administer as prescribed; monitor patient for adverse reactions; be aware of potential QT prolongation.

Evaluation: Assess reduction in nausea and vomiting; monitor ECG if indicated.

Patient/Family Teaching

Take medication exactly as prescribed.
Report any allergic reactions, dizziness, or severe headache.
Inform about potential for QT prolongation; avoid other QT-prolonging medications unless approved by healthcare provider.

Special Considerations

Black Box Warnings:

QT prolongation and serious arrhythmias, including Torsades de Pointes.
Serotonin syndrome when combined with other serotonergic drugs.

Genetic Factors: No clinically significant genetic considerations reported.

Lab Test Interference: No known interference.

Overdose Management

Signs/Symptoms: Dizziness, severe headache, weakness, hypotension, arrhythmias.

Treatment: Supportive care; monitor cardiac status; administer activated charcoal if ingestion is recent; consider overdose-specific treatments as per hospital protocol.

Storage and Handling

Storage: Store at room temperature 20-25°C (68-77°F), protected from light.

Stability: Stable when stored properly; use within the date on the label.