Drugs Q & A

Does Zofran Make You Sleepy?

Sleepiness refers to feeling drowsy or tired or being unable to keep your eyes open. Sleepiness can be accompanied by lethargy, weakness, and lack of mental agility. While most people feel drowsy at some point or another, persistent sleepiness or fatigue, especially at inappropriate times, can indicate a sleep disorder or other medical problem.

Many medications, especially tranquilizers, and sleeping pills, list drowsiness as a possible side effect. These medications have a label that warns against driving or operating heavy machinery while using these drugs.

What is Zofran?

Zofran is a brand of ondansetron, a medication used to prevent nausea and vomiting caused by cancer chemotherapy, radiation therapy, or surgery. It is also effective for treating gastroenteritis. It can be given by mouth or by injection into a muscle or into a vein.

How to use Zofran

To prevent nausea from chemotherapy, take this medication by mouth usually within 30 minutes before treatment begins. To prevent nausea from radiation treatment, take this medication by mouth 1 to 2 hours before the start of your treatment. To prevent nausea after surgery, take ondansetron by mouth 1 hour before the start of surgery. This medication may be taken with or without food. However, your doctor may tell you not to eat before chemotherapy, radiation, or surgery.

If you are using the liquid form of this medication, use a special measuring spoon or device to measure out your prescribed dose. Do not use a household spoon because you may not get the correct dose.

Take any other doses as directed by your doctor. Ondansetron may be taken up to 3 times a day for 1 to 2 days after your chemotherapy or radiation treatment is finished. If you are taking this medication on a prescribed schedule, take it regularly in order to get the most benefit from it. To help you remember, take it at the same time each day.

Dosage is based on your medical condition and response to therapy. The dosage for children may also be based on age and weight. The usual maximum dose in patients with severe liver problems is 8 milligrams in 24 hours. Take this medication exactly as directed. Do not take more medication or take it more often than prescribed. Ask your doctor or pharmacist if you have questions.

Does Zofran Make You Sleepy?

Yes, Zofran can cause sleepiness or drowsiness because it belongs to a class of medication called 5-HT3 (serotonin) receptor antagonist which modulates serotonin activity thereby aiding sleep regulation, especially REMS sleep regulation which plays an important role in dreaming, memory, emotional processing, and healthy brain development.

The sleep effect of Zofran can set in pretty quickly. Many people report feeling sleepy within about 1 hour of taking the medication. Zofran reaches maximum blood concentrations in about 2 hours. The effects of Zofran can last anywhere between 8 to 12 hours.

What are the side effects of Zofran?

Side effects of Zofran include:

•          anxiety

•          cold sensation

•          constipation

•          diarrhea

•          dizziness

•          drowsiness

•          elevated liver function test results

•          fever

•          gynecologic disorder

•          headache

•          injection-site pain

•          malaise or fatigue

•          numbness and tingling

•          poor oxygenation

•          severe itching

•          urinary retention

Other side effects of Zofran include:


•          heart rate irregularities (including ventricular and supraventricular tachycardia, premature ventricular contractions, and atrial fibrillation)

•          slow heart rate

•          electrocardiographic alterations (including second-degree heart block, QT/QTc interval prolongation, and ST segment depression)

•          palpitations

•          fainting (rarely and predominantly with intravenous ondansetron)

•          transient ECG changes including QT/QTc interval prolongation have been reported.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Zofran?

Zofran can cause a serious heart problem, especially if you use certain medicines at the same time, including antibiotics, antidepressants, heart rhythm medicine, antipsychotic medicines, and medicines to treat cancer, malaria, HIV, or AIDS. Tell your doctor about all medicines you use, and those you start or stop using during your treatment.

Taking ondansetron while you are using certain other medicines can cause high levels of serotonin to build up in your body, a condition called “serotonin syndrome,” which can be fatal. Tell your doctor if you also use:

•          medicine to treat depression;

•          medicine to treat a psychiatric disorder;

•          a narcotic (opioid) medication; or

•          medicine to prevent nausea and vomiting.

This list is not complete and many other drugs can interact with Zofran. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Give a list of all your medicines to any healthcare provider who treats you.


Dr. Oche Otorkpa PG Cert, MPH, PhD

Dr. Oche is a seasoned Public Health specialist who holds a post graduate certificate in Pharmacology and Therapeutics, an MPH, and a PhD both from Texila American University. He is a member of the International Society of Substance Use Professionals and a Fellow of the Royal Society for Public Health in the UK. He authored two books: "The Unseen Terrorist," published by AuthorHouse UK, and "The Night Before I Killed Addiction."
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