We’ve all been told to avoid mixing alcohol and antibiotics, but heeding that is another story.
But why is this the case? Besides getting really drunk and forgetting to take your meds. Can drinking while taking antibiotics make you sicker than you already are? Does it change the effectiveness of the drugs we take for better or for worse? Is it really that important?
Distilling the science behind how alcohol and antibiotics interact in the body.
Let’s get into the spirit – what is alcohol?
Widely, alcohol is a class of organic compounds that have one or more hydroxyl groups attached to a hydrocarbon chain. These are strange chemical terms, but a hydrocarbon chain only contains carbon and hydrogen atoms – think of the carbon atoms like the metal links of a bracelet, the hydrogen atoms branching out like charms.
A hydroxyl group is a hydrogen atom bonded to an oxygen atom, itself bonded to a carbon atom in the hydrocarbon chain.
Alcohol is used in solvents, hand sanitizers and cosmetics, but the specific alcohol found in the beverages we consume is called ethanol – or ethyl alcohol – which means the hydrocarbon chain only contains two carbons. Ethanol is made when sugars, usually from grains, fruits and vegetables, are fermented by single-celled organisms called yeast.
Bottom up! alcohol in the body
When alcohol is ingested, a small amount is immediately broken down or metabolized in the stomach into acetaldehyde. But most of the remaining alcohol is absorbed into the bloodstream, through the stomach and upper small intestine, and makes its way to the liver for the first time.
Once it arrives, only a small amount of alcohol is metabolized, while the rest leaves the liver, enters the general circulation, and is distributed through body tissues. This is called “first pass metabolism”.
Then the remaining alcohol returns to your liver to be metabolized a second and final time by several enzymes, which are proteins that catalyze biochemical reactions, the most important of which are here alcohol dehydrogenase and Cytochrome P450.
These enzymes and others downstream break down the alcohol until the carbon dioxide and water leave your body.
Alcohol should not cause problems when taking many common antibiotics
Antibiotics are substances used to treat bacterial infections by killing bacteria or preventing them from growing. Inside the body, antibiotics are either eliminated in their active form by the kidneys or metabolized by the liver.
A 2020 exam of all available scientific evidence behind alcohol-antibiotic interactions was reviewed across 87 studies to determine the evidence behind the alcohol warnings issued for many common antibiotics. But they found that drinking alcohol shouldn’t cause problems when taking a number of different common antibiotics.
The available data confirm that some specific antibiotics, and more broadly a few selected classes of antibiotics, show no adverse interactions when taken with alcohol.
For example: oral penicillins, the antibiotics cefdinir and cefpodoxime (from the class of antibiotics called cephalosporins), the class of broad-spectrum antibiotics called fluoroquinolones, and the antibiotics azithromycin and tetracycline.
But alcohol can still interact with some antibiotics
Alcohol can interact with medications two different ways. Pharmacokinetic interactions occur when alcohol interferes with the metabolism of a drug or the drug interferes with the metabolism of alcohol.
This usually happens in the liver where alcohol and some antibiotics are metabolized, sometimes even by the same enzymes.
In people who consume alcohol occasionally, a component of cytochrome P450 metabolizes only a small fraction of the alcohol ingested, but its activity can be increased tenfold in chronic heavy drinkers who consume 3 to 4 standard drinks per day.
When sober, this increased activity can increase the rate of antibiotic degradation, and when intoxicated alcohol competes with the antibiotic to metabolize and antibiotic degradation is slowed.
The second type of interactions is pharmacodynamic, where alcohol enhances the effects of a drug or vice versa.
Erythromycin, an antibiotic, is used to treat a wide variety of bacterial infections. But it also increases gastric contractions and speeds up stomach emptying, which means it can reduce the first-pass metabolism of alcohol and lead to faster absorption of alcohol in the small intestine.
In fact, the peaks in alcohol concentration were found be higher after taking erythromycin, increasing by 40% on average. Unfortunately, alcohol also decreases the effectiveness of erythromycin.
Don’t Forget Disulfiram-Like Reactions
There are also antibiotics that can unexpectedly trigger a disulfiram-like reaction when mixed with alcohol.
Disulfiram is a treatment for heavy drinking. It inhibits an enzyme important for alcohol metabolism, which causes a toxic by-product of alcohol metabolism to rapidly build up in the blood. This causes unpleasant effects including facial flushing, nausea, headache, vomiting, chest pain, dizziness, sweating, thirst, blurred vision and low blood pressure.
Unfortunately, the reaction occurs with uncertain frequency and varying severity across many antibiotics – so it’s not as simple as avoiding one or more major classes of antibiotics.
Ultimately, as with all medications, it’s important to talk openly with your own healthcare provider about the potential effects of mixing alcohol and antibiotics on you.