Ondansetron

Overview

It blocks serotonin signals that trigger vomiting. Providers also use it off-label for stomach bugs.

What it's used for

• Nausea and vomiting from chemotherapy or radiation
• Nausea after surgery
• Off-label: vomiting from stomach bugs

How to take it

• Take it with or without food.
• Dissolving tablets go on the tongue; don't swallow them whole. Handle them with dry hands.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

• Headache
• Constipation
• Tiredness

Warnings

• Tell your provider about heart rhythm problems or low potassium or magnesium.
• Vomiting with severe belly pain or swelling, or vomiting that won't stop, needs checking.

Other medicines, foods, and alcohol

• Apomorphine must not be taken with it.
• Other serotonin medicines raise the risk of serotonin syndrome.
• Other medicines that affect heart rhythm add to that risk.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Sometimes used for severe nausea in pregnancy. Talk with your provider about benefits and risks.

Missed doses, overdose, and storage

If you miss a dose

This medicine is often taken only when needed. If you take it on a schedule, take a missed dose when you remember, unless it's almost time for the next one. Don't double up.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

• Viral gastroenteritis (stomach bug)
• Food poisoning