Antibiotics and Alcohol

It is common to see “Avoid Alcohol” labels on prescription bottles. Many patients are concerned about mixing antibiotics with alcohol contained in beverages or other medications. In general, most antibiotics can be taken safely with small amounts of alcohol. Drinking excessive amounts of alcohol while fighting an infection may not be wise, can lead to dehydration, and may hinder the body’s natural ability to heal itself, as well.
In general, alcohol should be avoided when taking these antibiotics. Many over-the-counter medications (OTCs), such as cough or cold syrups may also contain alcohol in the formulation. The inactive ingredient listing can be checked to determine if alcohol is present, the label on the OTC bottle can be checked, or ask your physician or pharmacist. Prescription medications may also contain alcohol. Patients should check with their physician or pharmacist each time they receive a new prescription to determine if there are important drug interactions. A drug interaction checker to review drug combinations can give additional information.

One of the most common alcohol-antibiotic interactions is with the antimicrobial agent metronidazole (Flagyl). Metronidazole is used for a variety of infections, including gastrointestinal, skin, joint and respiratory tract infections. Taking metronidazole with alcohol may result in a reaction called a “disulfiram-like reaction”. A “disulfiram-like reaction” may include nausea, flushing of the skin, stomach cramps, vomiting, headaches, rapid heart rate, and difficulty breathing.[1] A similar reaction may occur with other antibiotics.

Certain antibiotics may also lead to central nervous system (CNS) side effects, such drowsiness, sedation, dizziness or confusion. Alcohol is also considered a CNS depressant. When alcohol is combined with antibiotics that also have a CNS depressant effect, additive effects may occur. These effects can be serious if driving, in the elderly, and in patients who may take other CNS depressant medications, such as opioid pain relievers, anxiety or seizures medications, among others.

Alcohol is metabolized (broken down) in the liver by an enzyme called cytochrome P450 2C9. Some drugs are also metabolized by the 2C9 enzyme. Depending upon how often and how much alcohol is consumed, this enzyme may affect how drugs are metabolized. When an intoxicating, acute amount of alcohol is consumed, the 2C9 enzyme is “inhibited”, meaning that it cannot metabolize drugs that require this enzyme as efficiently as normal. The levels of the drug in the body may increase because it is not fully metabolized and excreted. This could lead to drug toxicity and side effects. Alternatively, when alcohol is abused chronically, as may occur with an alcoholic, levels of the 2C9 enzyme may become “induced”, meaning that metabolizing is occurring at a more efficient rate, and drug levels may decrease. The therapeutic effect that is desired may not occur with lowered drug levels in the body.