Flagyl is the brand name of metronidazole, an antibiotic used to treat a variety of infections, from stomach ulcers to meningitis. (Metronidazole is also found in some other brand name antibiotics, including ; check your antibiotic's label.) Most of Flagyl's side effects are run-of-the-mill, such as nausea and vomiting. However, Flagyl is reported to interact dangerously with another common drug: alcohol.
Drinking even a small amount of alcohol (ethanol) while taking Flagyl can make a person very sick. Flagyl and alcohol together cause severe nausea and vomiting, flushing, fast heartbeat (tachycardia), and shortness of breath. The reaction has been described as being similar to the effects of Antabuse, a drug that treats alcoholism by causing patients to become very sick when they drink.
Obviously, beverages containing alcohol should not be consumed during treatment with Flagyl, but small amounts of alcohol can be found in hidden sources as well. Some kinds of mouthwash and cold medicine contain alcohol. Small amounts may also be served at religious services. Patients should avoid all of these alcohol sources while taking Flagyl and for 48 hours following the end of treatment.