According to MedlinePlus, metronidazole treats infections of the reproductive and gastrointestinal systems, vagina, skin and other areas of the body. The drug works by eliminating bacteria and other microorganisms, but does not treat viral infections such as colds or the flu.
Before taking metronidazole, MedlinePlus advises you to provide your doctor with a medication and allergy list so that interactions can be checked. Doctors must know if you have a history of Crohn's disease, or blood, liver or kidney disease. Patients taking metronidazole should not drink alcohol because it may lead to upset stomach, vomiting, headache, stomach cramps, sweating and redness of the face. Metronidazole sometimes makes skin more sensitive to the sun. Sunscreen, sunglasses and protective clothing are advised if sun exposure cannot be avoided. Women who are pregnant, plan to become pregnant or are breastfeeding should consult a doctor before starting metronidazole.
MedlinePlus explains that metronidazole can cause side effects such as vomiting, diarrhea, upset stomach, loss of appetite, dry mouth, metallic taste in the mouth, dark urine, irritated mouth or tongue, and numbness or tingling of the hands or feet. Symptoms such as rash, itching, stuffy nose, fever and joint pain require an immediate call to the doctor.