Zofran (ondansetron)

Health and Nutrition > Medicines > Z



How does it work?

Zofran tablets, syrup and injection all contain the active ingredient ondansetron hydrochloride dihydrate, which is a type of medicine called a 5HT3 antagonist. (NB. Ondansetron is also available without a brand name, ie as the generic medicine.) Ondansetron is used to prevent and treat nausea and vomiting that can be caused by chemotherapy or radiotherapy treatment for cancer, or by surgery.

Vomiting is controlled by an area of the brain called the vomiting centre. The vomiting centre is responsible for causing feelings of sickness (nausea) and for the vomiting reflex. It is activated when it receives nerve messages from another area of the brain called the chemoreceptor trigger zone (CTZ) and when it receives nerve messages from the gut.

Chemotherapy, radiotherapy and surgery can cause a substance called serotonin (5HT) to be released in the gut. This 5HT acts on the 5HT3 receptors that are found in the gut and causes nerve messages to be sent to the vomiting centre.

5HT released by chemotherapy, radiotherapy and surgery also activates the 5HT3 receptors that are found in the CTZ in the brain, causing further messages to be sent to the vomiting centre.

Ondansetron works by blocking the 5HT3 receptors that are found in the brain and gut. This prevents the nausea messages being sent from these areas to the vomiting centre. Ondansetron therefore prevents nausea, retching and vomiting that can otherwise occur following surgery or due to cancer treatments.

Ondansetron can be given by mouth (Zofran tablets or syrup), by injection into a muscle or vein, by drip into a vein (intravenous infusion), or by suppository (see the Zofran suppositories factsheet linked at the end of this factsheet).

What is it used for?

- Preventing and treating nausea and vomiting caused by chemotherapy or radiotherapy for cancer
- Preventing and treating nausea and vomiting following surgery.

Use with caution in

- Allergy to other 5HT3 antagonists, eg granisetron
- Decreased liver function
- Blockage of the gut (intestinal obstruction)
- Disurbances of the levels of salts (electrolytes) such as potassium, sodium and magnesium in the blood
- History of heart problems
- Irregular heart beats (arrhythmias)
- People taking medicines to treat an irregular heart beat (antiarrhythmics) or beta-blocker medicines.

Not to be used in

- Known hypersensitivity or allergy to any ingredient.

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy. If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and Breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

- The safety of this medicine during pregnancy has not been established. It is not recommended for use in pregnant women unless considered essential by your doctor. Seek medical advice from your doctor.
- This medicine may pass into breast milk. Mothers who need to take this medicine should not breastfeed their infants during treatment. Seek medical advice from your doctor.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

- Headache
- Constipation
- Flushing
- Hiccups
- Allergy to active ingredient (hypersensitivity)
- Involuntary movements
- Alteration in results of liver function tests
- Low blood pressure (hypotension)
- Chest pain
- Slow heart rate (bradycardia)
- Abnormal heart beats (arrhythmias)
- Seizures

The side effects listed above may not include all of the side effects reported by the drug's manufacturer. For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to ensure that the combination is safe.

The following medicines may increase the removal of ondansetron from the body and could therefore make it less effective:

- carbamazepine
- phenytoin
- rifampicin.

Small studies suggest that ondansetron may reduce the painkilling effect of tramadol.

The documents contained in this web site are presented for information purposes only. The material is in no way intended to replace professional medical care or attention by a qualified practitioner. The materials in this web site cannot and should not be used as a basis for diagnosis or choice of treatment. Conditions for use © Copyright 1998 - 2009 NetDoctor.co.uk - All rights reserved