SIDE EFFECTS: See also Warning section. Nausea and 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 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 you have any serious side effects, including: headache, vision changes, mental/mood changes (such as depression, thoughts of suicide). Although unlikely, when ketoconazole is used at high doses, it may cause an adrenal gland problem (adrenal insufficiency), a decrease in testosterone levels, and a decrease in sperm production. Ketoconazole can also worsen existing adrenal gland function problems (See also Precautions section). The adrenal gland problem may make it more difficult for your body to respond to physical stress. Therefore, before having surgery or emergency treatment, or if you get a serious illness/injury, tell your doctor or dentist that you are using this medication. Your doctor may order a blood test to monitor your adrenal gland function while you are taking ketoconazole. These effects usually go away after ketoconazole treatment is stopped. Tell your doctor right away if you have any serious side effects, including: unusual tiredness, weakness, dizziness upon standing, diarrhea, weight loss, menstrual period changes, decreased sexual interest or ability, enlarged/tender breasts in men. Get medical help right away if any of these rare but serious side effects occur: fast/irregular heartbeat, severe dizziness, fainting. A very serious allergic reaction to this drug is rare. However, get medical help right away 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: See also Side Effects section. Before taking ketoconazole, tell your doctor or pharmacist if you are allergic to it; or to other azole antifungal drugs (such as fluconazole, itraconazole); 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: liver problems, alcohol use, low testosterone levels, decreased adrenal gland function problems (such as low cortisol levels, Addison's disease, adrenal insufficiency), little or no stomach acid production (achlorhydria). Ketoconazole may cause a condition that affects the heart rhythm (QT prolongation). QT prolongation can rarely cause 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 ketoconazole, 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 ketoconazole safely. Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). Do not drink alcoholic beverages while taking this medication because alcohol increases the risk of serious liver problems. Avoiding alcoholic beverages will also decrease the risk of a rare reaction with ketoconazole that may result in flushing, headache, and nausea. Older adults may be more sensitive to the side effects of this drug, especially QT prolongation (see above). During pregnancy, this medication should be used only when clearly needed. It may cause harm to an unborn baby if taken during the first 3 months of pregnancy. Discuss the risks and benefits with your doctor. This medication passes into breast milk. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: See also Warning and How to Use sections. Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval. Ketoconazole interacts with many prescription and nonprescription drugs. While you are taking ketoconazole, it is very important to tell your doctor or pharmacist of any changes in medications that you are taking. Some products that may interact with this drug include: other drugs that can cause liver problems (such as acetaminophen). Other medications can affect the removal of ketoconazole from your body, which may affect how ketoconazole works. Examples include isoniazid, nevirapine, rifamycins (such as rifabutin, rifampin), St. John's wort, among others. This medication can slow down the removal of many other medications from your body, which may affect how they work. Examples of affected drugs include some benzodiazepines (such as alprazolam, midazolam, triazolam), domperidone, eletriptan, eplerenone, ergot drugs (such as ergotamine), nisoldipine, drugs used to treat erectile dysfunction-ED or pulmonary hypertension (such as sildenafil, tadalafil), some drugs used to treat seizures (such as phenytoin), some statin drugs (such as atorvastatin, lovastatin, simvastatin), among others. Ketoconazole requires acid in the stomach to be well absorbed. Therefore, if you are taking drugs that decrease the amount of stomach acid including antacids, heartburn/ulcer drugs (H2 blockers such as cimetidine, famotidine, ranitidine), sucralfate, or if you are taking drugs that slow down gut movement (anticholinergics such as dicyclomine, propantheline), take ketoconazole at least 2 hours before any of these drugs. If you are taking proton pump inhibitors (PPIs such as lansoprazole, omeprazole), ask your doctor or pharmacist for advice on how to reduce or avoid this interaction.

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.