The Dangers of Flagyl and Alcohol Interaction

Alcohol drinks, Image from Wikimedia CommonsIt has long been thought of that consuming alcohol while taking Flagyl causes adverse reactions in the body. However, this popular notion of Flagyl and alcohol interaction is being debunked by recent researches. Find out in this article if mixing Flagyl and alcohol together can really makes a person sick.

Overview of Alcohol and Flagyl (Metronidazole) Interaction

Flagyl is the brand name for the drug metronidazole, an antibiotics used to treat infections caused by anaerobic bacteria and protozoa such as bacterial vaginosis, pelvic inflammatory disease, pseudomembranous colitis, peptic ulcer disease, and among others. The drug is marketed in the U.S. by Pfizer, globally by Sanofi-Aventis (still under the Flagyl brand name), and by different generic manufacturers.

Common side effects of Flagyl include nausea, diarrhea, and metallic taste of the mouth. There are people who reported on the adverse effects of taking Flagyl and alcohol together. These people who consumed alcohol (even in small amounts) while taking Flagyl experienced severe nausea, vomiting, flushing of the skin, trachycardia (fast heartbeat), and shortness of breath. These symptoms are very similar to the effect of taking alcohol while taking Antabuse (disulfiram), a drug used to treat alcoholism by causing patients to become ill when they drink.

People who are under Flagyl medication should also avoid using products that contain alcohol such as mouthwash and cold medicine. Some kind of food contain small amount of alcohol since alcohol is being used in cooking; they should be avoided while under medication. It is usually advised to patients under Flagyl therapy not to drink alcohol for at least 48 hours after completion of treatment.

Flagyl and alcohol reaction is being questioned as an established pharmacologic fact because significant clinical evidences are lacking.


What causes the bad reaction of Flagyl and alcohol interaction in the body?

Because alcohol-Flagyl body reactions (e.g. nausea, trachycardia, flushing, etc.) are similar to alcohol-Antabuse reactions, scientists originally presumed that they work in the same manner. Antabuse (disulfiram) works by inhibiting the second step in alcohol metabolism in the liver. The first step is the break down of ethanol (alcohol) into acetaldehyde and the second step is the break down of acetaldehyde into acetic acid. Since Antabuse inhibits the second step, acetaldehyde will build up in the blood causing vomiting, flushing, trachycardia, etc.

A recent clinical research found out that metronidazole does not inhibit the breakdown of acetaldehyde in the liver and there is no significant increase in blood level of acetaldehyde when metronidazole and alcohol are taken together. The researchers said that a different mechanism may be at work. Karamanakos and colleagues (2007) suggested that the reactions may be due to increase serotonin level in the brain when Flagyl is taken; they have observed this scenario in the laboratory rats.

Visapaa et al. (2002) reported that Flagyl-alcohol reaction may not be as common as previously thought because there are only ten human case reports on the problem. However, the researchers noted that it is possible that Flagyl-alcohol reaction occur in subgroups of people so it is still advised not to drink while under Flagyl medication.

In an online forum on Flagyl-alcohol interaction, few people said that they didn’t experience any adverse effect on mixing Flagyl and alcohol. However, some of the people reported that drinking even small amount of alcohol or exposed to alcohol-containing products, experienced adverse reactions.[ad#afterpost]


Visapää, J. P. et al., “Lack of disulfiram-like reaction with metronidazole and ethanol.” Annals of Pharmacotherapy 2002 Jun; 36(6):971-974. Retrieved Jan. 29, 2010.

Karamanakos, P. N. et al.,”Pharmaceutical agents known to produce disulfiram-like reaction: effects on hepatic ethanol metabolism and brain monoamines.” International Journal of Toxicology 2007 Sep-Oct; 26(5):423-432. Retrieved Jan 29, 2010.


The information in this article is not a substitute for professional medical advice. Please seek advice from your doctor before taking any action suggested on this article.