Zofran (ondansetron) is a potent 5-HT3 receptor antagonist specifically engineered for the management and prevention of nausea and vomiting. It is a cornerstone therapeutic agent in clinical settings, most notably utilized to mitigate the emetogenic effects of chemotherapy, radiotherapy, and postoperative recovery. Its mechanism of action provides a targeted approach, offering patients significant relief and improving quality of life during challenging medical treatments. This medication is available in various formulations to suit individual patient needs and clinical scenarios.

Features

• Active Pharmaceutical Ingredient: Ondansetron hydrochloride.
• Drug Class: Selective 5-HT3 (serotonin) receptor antagonist.
• Available Formulations: Oral tablets (4mg, 8mg), orally disintegrating tablets (4mg, 8mg), oral solution (4mg/5mL), and injectable solution for intravenous or intramuscular use (2mg/mL).
• Mechanism: Works by blocking serotonin, a natural substance in the body that can trigger nausea and vomiting, both in the central nervous system (chemoreceptor trigger zone) and the periphery (GI tract).
• Onset of Action: Injectable form acts within minutes; oral formulations typically provide relief within 1-2 hours.
• Duration of Effect: Provides antiemetic protection for up to 24 hours following a single dose.

Benefits

• Provides highly effective prophylaxis and treatment for acute nausea and vomiting induced by highly emetogenic chemotherapy (HEC) and moderately emetogenic chemotherapy (MEC).
• Significantly reduces the incidence and severity of postoperative nausea and vomiting (PONV), facilitating smoother recovery and potentially earlier discharge.
• Offers a flexible dosing regimen with multiple administration routes (IV, IM, oral) to accommodate patient status, from critically ill to ambulatory.
• Helps patients maintain hydration and nutritional intake by controlling emesis, which is critical for treatment tolerance and overall outcomes.
• The availability of orally disintegrating tablets (ODTs) is particularly beneficial for patients who have difficulty swallowing or are experiencing active nausea.
• Contributes to improved patient compliance with difficult medical regimens by managing a primary side effect that often leads to treatment discontinuation.

Common use

Zofran is indicated for the prevention of nausea and vomiting associated with initial and repeat courses of emetogenic cancer chemotherapy, including high-dose cisplatin. It is also used for the prevention and treatment of postoperative nausea and vomiting. While not a primary indication, it is sometimes used off-label for the management of severe nausea and vomiting in other conditions, such as gastroenteritis, under a physician’s careful direction.

Dosage and direction

Dosage is highly dependent on the emetogenic potential of the chemotherapy regimen or the surgical procedure and the patient’s risk factors.

• Chemotherapy-Induced Nausea and Vomiting (Adults):
  • A common regimen is 8 mg or 0.15 mg/kg administered intravenously over 15 minutes, beginning 30 minutes before the start of emetogenic chemotherapy. This is followed by two additional 8 mg doses orally, 4 and 8 hours after the first dose. Then, 8 mg orally every 12 hours for 1 to 2 days after chemotherapy completion.
• Postoperative Nausea and Vomiting (Adults):
  • For prevention, 16 mg orally or 4 mg undiluted IV injection administered over 2-5 minutes immediately before induction of anesthesia.
  • For treatment, 4 mg IV or IM may be administered.
• Pediatric Patients:
  • Dosing for pediatric patients (ages 4-18) is based on body surface area or weight for chemotherapy and weight for postoperative use. Must be determined by a healthcare provider.
• Administration Note: The IV formulation should not be mixed with alkaline solutions. For IV infusion, it is compatible with common infusion fluids such as 5% Dextrose Injection, 0.9% Sodium Chloride Injection, and others. Oral tablets can be taken with or without food.

Always follow the specific dosage and schedule prescribed by the treating physician, as it will be tailored to the individual’s clinical situation.

Precautions

• ECG monitoring is recommended in patients with underlying heart conditions, electrolyte abnormalities (e.g., hypokalemia, hypomagnesemia), or those on concomitant medications that prolong the QT interval, as ondansetron may increase the risk of QT prolongation.
• Use with caution in patients with hepatic impairment. A single maximal daily dose of 8 mg is recommended in patients with severe hepatic impairment.
• This drug may mask a progressive ileus and/or gastric distention following abdominal surgery or in the presence of chemotherapy-induced gastroenteritis.
• Patients with phenylketonuria (PKU) should be advised that the orally disintegrating tablets contain aspartame, which is a source of phenylalanine.
• As with all antiemetics, Zofran is not intended for treatment of nausea of unknown etiology, as it may mask the symptoms of an underlying serious condition.

Contraindications

Zofran is contraindicated in patients:

• With known hypersensitivity to ondansetron or any components of the formulation.
• Receiving concomitant apomorphine, due to the risk of profound hypotension and loss of consciousness.
• With congenital long QT syndrome.

Possible side effect

The most commonly reported side effects are generally mild and transient.

• Very Common (>10%): Headache, constipation.
• Common (1-10%): Dizziness, fatigue, drowsiness, diarrhea, fever, sensation of cold, injection site reactions.
• Uncommon (0.1-1%): Flushing, hiccups, hypotension, chest pain, arrhythmias (including QT prolongation and rare cases of Torsade de Pointes).
• Rare (<0.1%): Blurred vision, transient visual disturbances (e.g., transient blindness), seizures, extrapyramidal reactions, anaphylaxis, liver enzyme abnormalities.

Drug interaction

Concomitant use of Zofran with other drugs that prolong the QT interval (e.g., certain antiarrhythmics like amiodarone, sotalol; antibiotics like erythromycin; antipsychotics like pimozide) may result in additive effects and a significant risk of serious arrhythmias. Ondansetron is metabolized by multiple hepatic cytochrome P-450 enzymes. Drugs that induce or inhibit these enzymes (e.g., rifampin, carbamazepine, phenytoin, tramadol) may alter its clearance and plasma levels. Use with apomorphine is contraindicated.

Missed dose

If a dose is missed for a scheduled prophylactic regimen (e.g., around chemotherapy), it should be taken as soon as it is remembered. However, if it is almost time for the next scheduled dose, the missed dose should be skipped, and the regular dosing schedule resumed. Do not double the dose to make up for a missed one. For acute treatment of nausea, take the dose when needed as directed by a physician.

Overdose

Symptoms of overdose may be an exaggeration of the known side effects, particularly visual disturbances, severe constipation, syncope, and dizziness. There is no specific antidote for ondansetron overdose. Management consists of supportive care, including continuous ECG monitoring due to the risk of QT prolongation.

Storage

• Store all formulations at controlled room temperature, 20°C to 25°C (68°F to 77°F).
• Protect from light.
• Keep the oral solution and tablets in their original container.
• Keep all medications out of the reach of children and pets.

Disclaimer

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any new treatment. Never disregard professional medical advice or delay in seeking it because of something you have read here.

Reviews

“Zofran was a game-changer during my chemotherapy. The nausea was debilitating after my first cycle, but with Zofran prophylaxis, I was able to manage the side effects and maintain my nutrition. The ODTs were a lifesaver when I couldn’t keep anything down.” – Oncology Patient

“As an anesthesiologist, Zofran is a first-line agent in our protocol for high-risk PONV patients. Its efficacy and safety profile are well-established, and it significantly improves the postoperative experience for our surgical patients.” – Medical Professional

“It worked incredibly fast for my child’s severe gastroenteritis. The pediatrician prescribed a single dose of the oral solution, and the vomiting stopped within the hour, allowing us to rehydrate her effectively.” – Parent