PRECAUTIONS: Before taking ondansetron, tell your doctor or pharmacist if you are allergic to it; or to other serotonin blockers (e.g., granisetron); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.Before using this medication, tell your doctor or pharmacist your medical history, especially of: irregular heartbeat, liver disease, stomach/intestinal problems (e.g., recent abdominal surgery, ileus, swelling).Ondansetron may cause a condition that affects the heart rhythm (QT prolongation). QT prolongation can infrequently result in serious (rarely fatal) fast/irregular heartbeat and other symptoms (such as severe dizziness, fainting) that need medical attention right away.The risk of QT prolongation may be increased if you have certain medical conditions or are taking other drugs that may cause QT prolongation. Before using ondansetron, tell your doctor or pharmacist of all the drugs you take and if you have any of the following conditions: certain heart problems (heart failure, slow heartbeat, QT prolongation in the EKG), family history of certain heart problems (QT prolongation in the EKG, sudden cardiac death).Low levels of potassium or magnesium in the blood may also increase your risk of QT prolongation. This risk may increase if you use certain drugs (such as diuretics/"water pills") or if you have conditions such as severe sweating, diarrhea, or vomiting. Talk to your doctor about using ondansetron safely.This drug may make you dizzy or drowsy. Do not drive, use machinery, or do any activity that requires alertness until you are sure you can perform such activities safely. Limit alcoholic beverages.To minimize dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.Older adults may be more sensitive to the side effects of this drug, especially QT prolongation (see above).This medication should be used only when clearly needed during pregnancy. Discuss the risks and benefits with your doctor.It is not known whether this drug passes into breast milk. Consult your doctor before breast-feeding.
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