Ondansetron belongs to the class of medications called 5-HT3 receptor antagonists. This medication is used to prevent nausea and vomiting associated with certain types of cancer chemotherapy and radiation. It is also used to prevent and treat the nausea and vomiting that occurs after surgery. It works by reducing the effects of a naturally-occurring chemical in the body called serotonin, which causes nausea and vomiting.
Each yellow, film-coated tablet, formed like a bean with “O” debossed on one side and “4” debossed on the other side, contains ondansetron 4 mg (as hydrochloride dihydrate). Nonmedicinal ingredients: cellulose microcrystalline, ferric oxide yellow, hypromellose, lactose monohydrate, magnesium stearate, maize starch (pregelatinized), and titanium dioxide.
Each yellow, film-coated tablet, formed like a bean with “O” debossed on one side and “8” debossed on the other side, contains ondansetron 8 mg (as hydrochloride dihydrate). Nonmedicinal ingredients: cellulose microcrystalline, ferric oxide yellow, hypromellose, lactose monohydrate, magnesium stearate, maize starch (pregelatinized), and titanium dioxide.
The recommended adult dose of ondansetron for nausea and vomiting caused by chemotherapy is based on severity of the symptoms and ranges from 8 mg to 24 mg daily given in divided doses.
Doses for children are based on body size. The recommended dose for children is 3 to 5 mg per square metre of body surface area and will be calculated by your doctor.
Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the one given here, do not change the way that you are taking the medication without consulting your doctor.
Ondansetron should be taken ½ to 1 hour before chemotherapy treatment. After this first dose, it should be taken every 8 to 12 hours for up to 5 days.
Use an oral syringe to measure each dose of the liquid, as it gives a more accurate measurement than household teaspoons.
The recommended adult dose of ondansetron to treat and prevent nausea and vomiting caused by radiation therapy is 8 mg taken by mouth, 1 to 2 hours before treatment, and then every 8 hours for up to 5 days after treatment.
The recommended adult dose of ondansetron to prevent nausea and vomiting caused by surgery is 16 mg taken by mouth, 1 hour before anesthesia. Alternatively a dose of 4 mg may be given by intravenous (into a vein) injection at the time of surgery. After surgery, a single dose of 4 mg of ondansetron may be given by intravenous injection to treat nausea or vomiting.
Ondansetron is not effective for treating or preventing nausea and vomiting caused by motion.
Store all forms of this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.
Do not take this medication if you:
Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.
The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.
Although most of the side effects listed below don’t happen very often, they could lead to serious problems if you do not seek medical attention.
Check with your doctor as soon as possible if any of the following side effects occur:
Stop taking the medication and seek immediate medical attention if any of the following occur:
Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.
Health Canada has issued new information concerning the use of Zofran (ondansetron). To read the full report, visit Health Canada’s website at www.hc-sc.gc.ca.
Allergy: People who have had an allergic reaction to dolasetron or granisetron are advised not to take ondansetron. Before you take ondansetron, inform your doctor about any previous adverse reactions you have had to medications. Contact your doctor at once if you experience signs of an allergic reaction such as skin rash, itching, difficulty breathing, or swelling of the face and throat.
Abnormal heart rhythms: Very rarely, ondansetron can affect the heart’s electrical activity and cause an irregular heartbeat. This is more likely to happen with the injectable form of ondansetron. Certain medications (e.g., sotalol, quinidine, thioridazine, chlorpromazine, droperidol, pimozide, gatifloxacin, moxifloxacin, mefloquine, pentamidine, arsenic trioxide, dolasetron mesylate, probucol, tacrolimus) can increase the risk of a type of abnormal heart rhythm called QT prolongation, and should not be used in combination with ondansetron. You are more at risk for this type of abnormal heart rhythm and its complications if you:
If you have heart disease and abnormal heart rhythms, or are taking certain medications (e.g., verapamil, atazanavir), discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Your doctor may monitor your heart rate using a test called an electrocardiogram (ECG) while you are using this medication.
Liver function: Ondansetron is broken down and removed from the body by the liver. Decreased liver function slows down the removal of the medication from the body and increases the risk of side effects from ondansetron. If you have liver disease or reduced liver function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
Motion sickness: Ondansetron is not effective for the treatment of motion sickness.
Neuroleptic malignant syndrome (NMS): Ondansetron, like other similar medications, can cause a potentially fatal syndrome known as neuroleptic malignant syndrome (NMS). If you notice the symptoms of NMS such as high fever, muscle stiffness, confusion or loss of consciousness, sweating, racing or irregular heartbeat, or fainting, get immediate medical attention.
Phenylketonuria: People with phenylketonuria (lacking the enzyme needed to break down phenylalanine) should take forms of ondansetron other than oral dissolving tablets (ODT). The ODT form of ondansetron contains aspartame, an ingredient that cannot be broken down in the body by people who have phenylketonuria.
Serotonin Syndrome: Severe reactions are possible when ondansetron is combined with other medications that act on serotonin, such as tricyclic antidepressants and serotonin reuptake inhibitors, medications used to treat depression. These combinations must be avoided. Symptoms of a reaction may include muscle rigidity and spasms, difficulty moving, changes in mental state including delirium and agitation. Coma and death are possible.
Pregnancy: The safety of ondansetron for use by pregnant women has not been established. This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.
Breast-feeding: It is not known if ondansetron passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.
Children: The safety and effectiveness of using this medication to treat nausea and vomiting caused by chemotherapy have not been established for children under 3 years of age. The safety and effectiveness of using this medication to treat nausea and vomiting caused by radiation or surgery have not been determined for children less than 18 years of age. Its use by this age group is not recommended.
Seniors: The safety and effectiveness of using this medication by people 65 years or older to treat nausea and vomiting caused by surgery have not been established. Seniors may be at an increased risk of developing irregular heart beat with ondansetron, particularly the injectable form. Talk to your doctor about any concerns you may have.
There may be an interaction between ondansetron and any of the following:
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