Ondansetron is a medication prescribed to prevent nausea and vomiting. The active ingredient is ondansetron, and markings such as “IC” on a tablet are imprint codes used by pharmaceutical companies to identify their version of the drug. This medication is a targeted therapy designed to manage symptoms from specific medical treatments and is not intended for all causes of nausea, such as motion sickness.
Medical Uses and Mechanism
Ondansetron’s primary uses are to prevent nausea and vomiting from cancer chemotherapy, radiation therapy, and post-operative recovery. These treatments can trigger the body’s vomiting reflex, and ondansetron is given proactively to manage these symptoms. It is prescribed for adults and children 4 years of age and older.
The medication functions by blocking serotonin, a chemical the body releases during stressors like chemotherapy or surgery. This chemical binds to 5-HT3 nerve receptors, sending signals to the brain that trigger nausea and vomiting. As a 5-HT3 receptor antagonist, ondansetron obstructs this process by interrupting the signals. This action prevents the symptoms from developing.
Dosage and Administration
Ondansetron is available as standard oral tablets, orally disintegrating tablets (ODT), and a liquid oral solution. The ODT form dissolves on the tongue without water, which is useful for patients who have difficulty swallowing pills. The prescribed form depends on the patient’s condition and ability to take medication.
The dosing schedule is timed to the medical procedure. For preventing nausea from chemotherapy, a dose is taken 30 minutes before treatment begins. For radiation therapy, it is taken 1 to 2 hours beforehand. For post-operative use, it is administered about an hour before anesthesia.
Patients must follow their healthcare provider’s instructions, as dosages can vary. An adult might take an 8 mg tablet before chemotherapy, followed by subsequent doses every 8 to 12 hours for a day or two. Dosages for children are calculated based on age and weight, and the maximum daily dose for patients with severe liver impairment is reduced to 8 mg.
Potential Side Effects
Common side effects of ondansetron include headache, a feeling of lightheadedness or dizziness, drowsiness, and constipation. Some individuals may also report feeling fatigued or experiencing a cold sensation. These reactions are generally mild and may lessen as the body adjusts to the medication.
Certain less common side effects indicate a more serious reaction requiring prompt medical attention. These include:
- Blurred vision or temporary vision loss
- Severe dizziness that leads to fainting
- A slow heart rate or difficulty breathing
- An allergic reaction, characterized by a rash, itching, or swelling of the face, tongue, or throat
A rare but serious condition called serotonin syndrome can occur if serotonin levels become too high. Symptoms include agitation, hallucinations, fever, a rapid heart rate, and gastrointestinal distress. Another consideration is that ondansetron may mask a developing intestinal blockage, so patients should monitor for decreased bowel activity.
Important Safety Considerations
Before taking ondansetron, discuss your full medical history with a healthcare provider. People with certain pre-existing conditions, such as liver disease, may need to use this medication with caution. A personal or family history of heart conditions, particularly Long QT syndrome, is also a concern as ondansetron can affect heart rhythm.
The medication can interact with other drugs. It should not be taken with apomorphine, a medication used for Parkinson’s disease. Caution is also advised when taking ondansetron with other medications that increase serotonin levels, such as certain antidepressants, as this can elevate the risk of serotonin syndrome. Drugs known to affect heart rhythm could also have their effects amplified.
The use of ondansetron during pregnancy and breastfeeding requires a discussion with a doctor to weigh the benefits against potential risks. While some studies have reviewed its use in pregnancy, the full scope of its effects is still under evaluation. It is not known if ondansetron passes into breast milk or what effect it might have on a nursing infant.