Will Alcohol Make Antibiotics Less Effective?

According to the Centers for Disease Control and Prevention's (CDC) 2020 annual report on outpatient antibiotic prescriptions, 201.9 million antibiotic prescriptions — equivalent to 613 antibiotic prescriptions per 1,000 people — were issued that year. Given the widespread use of antibiotics, it's important to understand what they are, how they work, and what substances interact negatively with them. 

The Merck Manual defines antibiotics as a class of drugs used to treat bacterial infections. Antibiotics either kill bacteria or inhibit their reproduction. Given that antibiotics target bacterial infections, it's important to note they have no impact on viral infections, such as the common cold or flu. In order to get the maximum benefits of an antibiotic prescription, it's imperative that the directions be followed and all warning labels are read carefully. One warning advises consumers not to take their medication while consuming alcohol and often lists potential side effects that may occur. 

Antibiotics can cause significant side effects, such as gastrointestinal upset, nausea, vomiting, anxiety, dizziness, and high blood pressure on their own (via GoodRx). Mixing alcohol with antibiotics can exacerbate these side effects, given alcohol causes gastrointestinal symptoms and loss of coordination, and can reduce the body's ability to fight infections (via Healthline). Alcohol raises the risk for adverse side effects caused by antibiotics, but does it decrease their effectiveness?

Alcohol consumption while taking antibiotics is generally frowned upon, specifically because mixing the two substances can lead to numerous negative side effects. The most common side effect is a "disulfiram-like reaction." This is caused by a process in the body that produces symptoms similar to when alcohol is consumed after taking disulfiram. Disulfiram is an oral drug used for treating alcoholism and causes undesirable physical symptoms when alcohol is consumed (via MedicineNet). Symptoms of a "disulfiram-like reaction" include headache, flushed skin, nausea, vomiting, chest pain, and rapid heart rate (via Drugs.com). 

Alcohol can also depress the central nervous system (CNS), and there are antibiotics that act as CNS depressants as well. When the two are combined, the CNS side effects are exacerbated. Patients who combine antibiotics and alcohol may experience side effects that range in severity, depending on the medication they are taking. When combined with oxazolidinones, for example, alcohol can lead to the following side effects — agitation, unusual sweating, rapid heartbeat, elevated blood pressure, altered mental status, vomiting, seizures, muscle spasms, and cardiorespiratory depression. Fluoroquinolones can cause potential mental health side effects, such as confusion and memory loss. When mixed with alcohol, nitroimidazoles can lead to a "disulfiram-like reaction" (via MedicalNewsToday).

Will alcohol impact an antibiotic's ability to fight infection? Apparently, the answer depends on what antibiotic you are taking. 

According to a 2020 article published in Antimicrobial Agents and Chemotherapy, certain antibiotics aren't impacted by the presence of alcohol, whereas others impacted efficacy. According to the article, the only antibiotic listed to have its efficacy negatively impacted by alcohol was doxycycline. When administered to rats as part of a liquid diet, it decreased the infection cure rate to 64.7% in alcohol-fed rats vs. 100% in those without. 

Doxycycline is a tetracycline derivative. These antibiotics may be used to treat infections caused by susceptible microorganisms, such as gram-positive and gram-negative bacteria, chlamydia, mycoplasma, protozoans, or rickettsiae (via Drugs.com). 

Conversely, levofloxacin, moxifloxacin, and trovafloxacin had improved efficacy in alcohol-fed rats, compared to alcohol-free rats. Levofloxacin, moxifloxacin, and trovafloxacin belong to a class of antibiotics known as fluoroquinolones. Fluoroquinolones proved equally effective at improving survival and had improved efficacy in alcohol-fed rats. Moxifloxacin supported increased efficacy in alcohol-fed rats, given those without alcohol showed dose-dependent survival. 

According to the article published in Antimicrobial Agents and Chemotherapy, currently, there is no data suggesting that alcohol impacts the efficacy of the following antibiotic classes: beta-lactams, macrolides, nitrofurantoin, nitroimidazoles, sulfa antibiotics, oxazolidinones, and antimycobacterials. Make sure to consult your pharmacist or physician regarding the interactions between your prescription and alcohol for beginning a course of antibiotics.