Ondansetron: Uses & Side Effects

Instructor: Alexandra Unfried

Alexandra earned her master's degree in nursing education and is currently a hospital supervisor/administrator.

Ondansetron is a medication that is classified as a serotonin 5-HT3 receptor antagonist. It blocks the action of serotonin. Read on to make sense of this information, as this lesson will discuss the uses of ondansetron and its side effects.

Nausea is not a good feeling, especially when already dealing with other medical issues. John relates to this too well. He is currently undergoing chemotherapy for lung cancer, and the treatments make him feel sick to his stomach. Luckily, his doctor has started him on ondansetron to help with his nausea before and after treatments.

Uses of Ondansetron

Ondansetron blocks the action of serotonin in the brain that is responsible for causing nausea and vomiting. It is used commonly for people undergoing cancer treatment such as chemotherapy and radiation therapy, as well as for people having surgery. This works well when taken before the treatment to decrease any nausea or vomiting that may occur as a side effect.

For example, a person who is going to have a scheduled toe amputation would be prescribed ondansetron to take one hour before the surgery in order to prevent nausea during recovery. Radiation therapy requires the person to take ondansetron one to two hours before treatment to prevent nausea. In the case of John, who is going through chemotherapy, he takes his ondansetron thirty minutes before each treatment. He also takes it up to three times a day for one to two days afterward.

Ondansetron can be taken with or without food and comes in several forms including tablet, rapidly dissolving tablet, and liquid. The dosage for ondansetron will be determined by the doctor, depending on the treatment for each situation. Some people take it regularly, while others only take it when needed. Dosages for children are usually based on weight, and you should not take more than 24 milligrams in twenty-four hours.

Ondansetron tablet

Side Effects of Ondansetron

As with most prescribed medications, there is a risk of many different side effects. Usually, the benefit of taking the medication will be greater than any mild side effects. However, you should notify your doctor if the side effects do not go away or get worse over time.

The most common side effects are:

  • Headache
  • Lightheadedness
  • Dizziness
  • Drowsiness
  • Tiredness
  • Constipation
  • Chills

Serious side effects are usually uncommon and rare but may occur. Your doctor must be informed immediately if there are any serious side effects. Not all of the serious side effects will be mentioned here, but any abnormal symptom or problem should be reported.

Examples of serious side effects include:

  • Stomach pain
  • Muscle spasms
  • Vision changes
  • Chest pain
  • Irregular heartbeat (including fast or slow heartbeat)
  • Severe dizziness
  • Fainting
  • Allergic reaction (rash, swelling, shortness of breath, hives, itching, difficulty swallowing)

While uncommon, signs and symptoms of an overdose of ondansetron include:

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