SIDE EFFECTS: Dizziness, headache, stomach upset, nausea, vomiting, loss of appetite, diarrhea, constipation, or metallic taste in your mouth may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly. This medication may cause your urine to turn darker in color. This effect is harmless and will disappear when the medication is stopped. 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 you have any serious side effects, including: signs of a new infection (such as sore throat that doesn't go away, fever), easy bruising/bleeding, stomach/abdominal pain, painful urination. Get medical help right away if you have any very serious side effects, including: unsteadiness, seizures, mental/mood changes (such as confusion), trouble speaking, numbness/tingling of arms/legs, eye pain, sudden vision changes, headache that is severe or doesn't go away, stiff/painful neck. Use of this medication for prolonged or repeated periods may result in oral thrush or a new yeast infection. Contact your doctor if you notice white patches in your mouth, a change in vaginal discharge, or other new symptoms. 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: Before taking metronidazole, tell your doctor or pharmacist if you are allergic to it; or to other antibiotics (such as tinidazole); 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 disease, kidney disease, certain blood disorders (low blood cell counts). People with a rare genetic disorder (Cockayne syndrome) may be at risk for very serious liver disease if they use metronidazole. Discuss the risks and benefits with your doctor. If metronidazole is used, your doctor will check your liver function. Get medical help right away if you have any signs of liver disease during treatment (such as nausea/vomiting that doesn't stop, loss of appetite, severe stomach/abdominal pain, yellowing eyes/skin, dark urine). Avoid alcoholic beverages and products containing propylene glycol while taking this medication and for at least 3 days after finishing this medicine because severe stomach upset/cramps, nausea, vomiting, headache, and flushing may occur. This drug may make you dizzy. Alcohol or marijuana can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Talk to your doctor if you are using marijuana. Metronidazole 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). 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. Discuss the risks and benefits with your doctor before breast-feeding. If you are prescribed the single-dose treatment, your doctor may direct you to stop breast-feeding for a short time after the dose. Consult your doctor for more details.

DRUG INTERACTIONS: See also Precautions section. 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. Some products that may interact with this drug include: alcohol-containing products (such as cough and cold syrups, aftershave), products containing propylene glycol, lopinavir/ritonavir solution, lithium. Do not take metronidazole if you are also taking disulfiram or if you have taken disulfiram within the last 2 weeks. Although most antibiotics are unlikely to affect hormonal birth control such as pills, patch, or ring, a few antibiotics (such as rifampin, rifabutin) can decrease their effectiveness. This could result in pregnancy. If you use hormonal birth control, ask your doctor or pharmacist for more details. This medication may interfere with certain lab tests, possibly causing false test results. Make sure lab personnel and all your doctors know you use this drug.

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. Symptoms of overdose may include: nausea, vomiting, unsteadiness.