SIDE EFFECTS: Headache, loss of appetite, upset stomach, or nausea/vomiting may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly. Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Tell your doctor right away if any of these unlikely but serious side effects occur: vision changes (such as blurred/decreased vision, color blindness), symptoms of liver disease (such as persistent nausea/vomiting, unusual tiredness/weakness, severe stomach/abdominal pain, yellowing eyes/skin, dark urine), numbness/tingling of arms/legs, toe/joint pain. Tell your doctor right away if any of these rare but serious side effects occur: mental/mood disorders (such as confusion, hallucinations), signs of a new infection (such as fever, persistent sore throat), easy bleeding/bruising. A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

PRECAUTIONS: Before taking ethambutol, tell your doctor or pharmacist if you are allergic to it; 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: eye problems (such as optic neuritis, cataracts, diabetic retinopathy), liver disease, kidney disease, alcohol use. Ethambutol may cause live bacterial vaccines (such as typhoid vaccine) to not work as well. Do not have any immunizations/vaccinations while using this medication unless your doctor tells you to. Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). Alcohol may increase the risk of liver disease. Avoid alcoholic beverages while using this medication. During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor. This medication passes into breast milk but is unlikely to harm a nursing infant. Consult your doctor before breast-feeding. If you have HIV disease, do not breast-feed because breast milk can transmit HIV.

DRUG INTERACTIONS: See also How to Use section. The effects of some drugs can change if you take other drugs or herbal products at the same time. This can increase your risk for serious side effects or may cause your medications not to work correctly. These drug interactions are possible, but do not always occur. Your doctor or pharmacist can often prevent or manage interactions by changing how you use your medications or by close monitoring. To help your doctor and pharmacist give you the best care, be sure to tell your doctor and pharmacist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products) before starting treatment with this product. While using this product, do not start, stop, or change the dosage of any other medicines you are using without your doctor's approval. Keep a list of all the products you use. Share the list with your doctor and pharmacist to reduce your risk for serious medication problems.

OVERDOSE: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center.