Home Drug Guide Ondansetron

Drug Guide

Generic Name

Ondansetron

Brand Names Zofran ODT, Zuplenz

Classification

Therapeutic: Antiemetic

Pharmacological: Serotonin 5-HT3 receptor antagonist

FDA Approved Indications

  • Nausea and vomiting induced by chemotherapy
  • Nausea and vomiting from radiotherapy
  • Postoperative nausea and vomiting

Mechanism of Action

Ondansetron selectively antagonizes serotonin 5-HT3 receptors located peripherally on vagal nerve terminals and centrally in the chemoreceptor trigger zone, preventing serotonin from binding and reducing nausea and vomiting signals.

Dosage and Administration

Adult: Typically 8 mg orally or IV 30 minutes before chemotherapy or surgery, repeated as needed. For postoperative nausea, 16 mg orally or IV prior to anesthesia.

Pediatric: Dose varies by weight and age; generally 8 mg orally or IV for children over 4 years, with specific dosing guidelines.

Geriatric: Use with caution; no specific dose adjustment, but monitor for adverse effects.

Renal Impairment: Adjusted dose may be necessary; consult specific guidelines.

Hepatic Impairment: Use with caution; dose adjustment recommended.

Pharmacokinetics

Absorption: Rapidly absorbed after oral administration; bioavailability approximately 62%

Distribution: Wide tissue distribution; crosses the blood-brain barrier

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

Excretion: Excreted primarily in urine and feces

Half Life: Approximately 3-6 hours

Contraindications

  • Known hypersensitivity to ondansetron or other 5-HT3 antagonists

Precautions

  • Use cautiously in patients with QT prolongation or electrolyte abnormalities
  • Monitor ECG in at-risk populations
  • Use during pregnancy only if clearly indicated
  • Lactation: Consider the benefits and risks; may pass into breast milk

Adverse Reactions - Common

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

Adverse Reactions - Serious

  • QT prolongation leading to Torsades de Pointes (Rare)
  • Serotonin syndrome (Rare)
  • Allergic reactions including anaphylaxis (Rare)

Drug-Drug Interactions

  • Other medications that prolong QT interval (e.g., certain antibiotics, antipsychotics)
  • Proton pump inhibitors may increase serum levels

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor for signs of hypersensitivity and cardiac arrhythmias; baseline and ongoing ECG if indicated.

Diagnoses:

  • Risk for electrolyte imbalance-related arrhythmias
  • Risk for nausea and vomiting

Implementation: Administer as prescribed; monitor heart rhythm; assess for adverse reactions.

Evaluation: Effectiveness in reducing nausea/vomiting; monitor for side effects.

Patient/Family Teaching

  • Take medication exactly as prescribed.
  • Report any chest pain, irregular heartbeat, or signs of allergic reactions.
  • Be cautious if feeling dizzy or headache occurs.
  • Do not operate machinery if feeling dizzy.

Special Considerations

Black Box Warnings:

  • QT prolongation and serious arrhythmias, including Torsades de Pointes

Genetic Factors: CYP2D6 poor metabolizers may have increased drug levels.

Lab Test Interference: None known.

Overdose Management

Signs/Symptoms: Dizziness, severe constipation, hypotension, fainting, or arrhythmias.

Treatment: Supportive, with ECG monitoring; treat arrhythmias accordingly; activated charcoal may be used if ingestion recent.

Storage and Handling

Storage: Store at room temperature, protected from moisture and light.

Stability: Stable for specified shelf life as per manufacturer instructions.

🛡️ 5 Critical Medication Safety Tips for Nurses

1

Triple-Check High-Risk Medications

Always have another nurse verify insulin, heparin, warfarin, and chemotherapy drugs. These "high-alert" medications cause the most serious errors. Check concentration, dose calculation, and pump settings twice.

2

Know Look-Alike, Sound-Alike Drugs

Common mix-ups: hydromorphone/morphine, Celebrex/Celexa, Zyprexa/Zyrtec. Always use BOTH generic and brand names, read labels twice, and use barcode scanning when available. One wrong letter can be fatal.

3

Assess Before AND After Giving Meds

Check vitals before cardiac meds, pain levels before analgesics, and blood glucose before insulin. Always reassess within 30 minutes to evaluate effectiveness and watch for adverse reactions.

4

Watch for Drug Interactions

Common dangerous combinations: warfarin + aspirin (bleeding), ACE inhibitors + potassium (hyperkalemia), digoxin + diuretics (toxicity). Always check drug interactions before administering new medications.

5

Educate Your Patients

Teach patients medication names, purposes, major side effects, and what to report. Informed patients catch errors and improve compliance. Always encourage questions - an educated patient is a safer patient.

⚡ Remember: When in doubt, don't give it out! It's always safer to double-check than regret later.

⚠️ Medical Disclaimer

This drug guide is for educational purposes only and is NOT intended for clinical use. Always consult current prescribing information, healthcare providers, and institutional protocols before administering any medication. Do not use this information for patient care decisions.