Flagyl | Metronidazole and Alcohol = Disaster!

People are often warned to avoid alcohol if they take certain medications. For example, anyone taking sedatives such as alprazolam (Xanax), clonazepam (Klonopin), diazepam (Valium) or lorazepam (Ativan) is often told not to drink alcoholic beverages. The additive effect could lead to substantial impairment. Metronidazole and alcohol are a different kind of problem. This interaction can be devastating, as this reader relates.

Metronidazole and Alcohol: An Unusual Interaction

Q. I once took a medication (metronidazole) that would make you sick if you drank alcohol with it. While I was on it, I went camping. Fueling the alcohol stove with denatured 100% ethanol, I spilled a lot of it on my hands. I did not drink any alcohol.

Later that night, I was violently ill with vomiting and diarrhea. My doctor was quite surprised when I told him about this reaction.

Why Do People Take Metronidazole (Flagyl)?

Metronidazole (Flagyl) is a somewhat unusual antibiotic that works differently from many other antibacterial drugs such as amoxicillin, azithromycin or cephalexin. Metronidazole is especially effective against anaerobic infections. Anaerobic bacteria can grow and thrive without oxygen. They actually have trouble multiplying when exposed to air.

Aerobic microorganisms thrive in an environment where there is oxygen. This gas permits aerobic bacteria to oxidize glucose and/or fat for energy.

Metronidazole works for a wide range of hard-to-treat bacterial and protozoal infections. They include:

Trichomoniasis vaginalis (that infects the vaginal tract, aka trichomoniasis)

Giardia lamblia (that causes misery in the digestive tract, aka giardiasis)

Entamoeba histolytica (that lead to amebic dysentery in the GI tract, aka amebiasis. This is a devastating condition! I have had it.)

Other nasties that metronidazole goes after include:

Gardnerella vaginalis
Helicobacter pylori
Clostridium difficile (clostridioides, aka C. diff)
Bacteroides fragilis

Metronidazole and Alcohol Interaction After Skin Absorption:

A. The symptoms you experienced are typical of an interaction between metronidazole and alcohol. They include nausea, stomach pain and cramps, vomiting and diarrhea. Headaches and flushing are sometimes part of that reaction. Other complications of this metronidazole and alcohol interaction may include low blood pressure, rapid pulse, heart palpitations and dizziness. Seizures may also result from the combination.

The metronidazole and alcohol interaction can persist for two to three days after the drug has been discontinued. That means means that people on metronidazole must avoid consuming alcohol for at least three days after they stop the medication. It takes a few days for the drug to be eliminated from the body.

Alcohol Absorbed Through the Skin?

Most doctors would probably be as surprised as yours was to learn that you might absorb enough alcohol through your skin to trigger symptoms. We recently asked the question:

Does Alcohol Get Into Your Body After Using Hand Sanitizers?

We were particularly concerned about reports that some alcohol-based (ethanol) hand sanitizers were contaminated with benzene. Here is a link to that article.

We describe the confusing and contradictory literature about alcohol absorption through the skin and drug interactions. In particular, we describe the potential interaction between alcohol and disulfiram (Antabuse). This drug is given to people with an alcohol-dependency problem to discourage drinking. It produces symptoms quite similar to the metronidazole and alcohol interaction.

The latest research on Alcohol Absorption Through the Skin:

We just discovered a fascinating study on the interaction between “alcohol-based hand rubs” (hand sanitizers) and disulfiram (Alcohol and Alcoholism, Jan. 4, 2021). The authors contacted patients who were prescribed disulfiram for alcohol use disorders:

“Among the 82 (24%) patients adherent to disulfiram, 42 (12.3%) were using alcohol-based hand rubs. Out of these, a total of eight patients (19%) had features suggestive of DER [disulfiram ethanol reaction].

“Patients on disulfiram should be advised to use alternate methods of hand hygiene.”

This suggests to me that getting ethanol-based fuel for a camp stove all over your hands could indeed trigger a metronidazole and alcohol interaction.