Ofmit

What It Is Used For

Ondansetron prevents and treats nausea and vomiting caused by cancer chemotherapy, radiotherapy and surgery. Doctors sometimes also use it for severe vomiting from other causes.

How to Take It

Your doctor will set the dose. A common adult dose for chemotherapy is 8 mg taken 1 to 2 hours before treatment, then 8 mg every 12 hours for up to 5 days. Children's doses depend on weight or body size. Mouth-dissolving tablets are placed on the tongue and allowed to melt; they do not need water.

Who Should Not Take It

Do not take it if you are allergic to ondansetron or similar medicines (such as granisetron), take apomorphine, or were born with a long QT heart rhythm problem.

Side Effects

Common: headache, constipation, a feeling of warmth or flushing, and tiredness. Rarely: irregular heartbeat, fits, or blurred vision. Get medical help straight away for chest pain, a racing or irregular heartbeat, fainting, or signs of an allergic reaction.

Precautions

Tell your doctor if you have a heart rhythm problem, low potassium or magnesium, liver disease (the daily dose is usually limited to 8 mg), or signs of a bowel blockage. Ondansetron can hide the symptoms of a blocked bowel after surgery.

Pregnancy and Breastfeeding

Avoid in the first 3 months of pregnancy unless your doctor advises it, because a small increase in the risk of cleft lip or palate has been reported. Ask your doctor before using it while breastfeeding.

Interactions

Do not take it with apomorphine. Taking it with antidepressants (SSRIs or SNRIs) or tramadol can rarely cause serotonin syndrome (agitation, sweating, shaking, fast heartbeat). Other medicines that affect heart rhythm add to the risk. Carbamazepine, phenytoin and rifampicin can make it work less well.

Storage

Store below 30°C, protected from light and moisture, out of the reach of children.