Keflex Cephalexin AlcoholThere is no drug interaction between cephalexin (Keflex) and alcohol, but it is not recommended to drink alcohol when recovering from an illness. The body needs plenty of rest and needs to stay hydrated during the illness. Alcohol can impair the immune system from fighting off infections and cause similar side effects as antibiotics, such as:

  • Dizziness
  • Nausea
  • Upset stomach


The amount of time the Keflex will last in the body depends on the individual. According to the prescribing information, most of the drug is cleared from the body within 8 hours for healthy individuals. For individuals with kidney or liver issues, this may take much longer.


If you want to avoid alcohol while taking the Keflex, it would be advised to wait at least 8 hours after your last dose before consuming alcohol. However, it would be wise to wait even longer if you have kidney or liver issues.


Information about Alcohol

The process of the body breaking down alcohol is completed by different proteins in the body, including alcohol dehydrogenase, aldehyde dehydrogenase, catalase, and cytochrome P450 (CYP2E1). In specific situations where the products of alcohol breakdown build up too much in the body, these effects can be severe and potentially fatal.


One of the products of the breakdown of alcohol (acetaldehyde) is usually what causes the unpleasant side effects. A build-up of acetaldehyde can cause effects such as:

  • Nausea
  • Vomiting
  • Flushing
  • Fast heart rate
  • Decreased blood pressure


Alcohol Interactions with Other Antibiotics

Although there is no interaction between alcohol and Keflex, it can interact with some other antibiotics to potentially cause a build-up of alcohol and products of alcohol breakdown, leading to unpleasant side effects.


The other antibiotics that can interact with alcohol include metronidazole, tinidazole, cefotetan, and sulfamethoxazole/trimethoprim.


Metronidazole (Flagyl) And Tinidazole (Tindamax)

Alcohol is contraindicated with metronidazole and should also not be used with tinidazole. Alcohol should not be used with or within 3 days after completing therapy with these antibiotics. Both of these can significantly increase side effects of alcohol. It isn't completely understood how this happens, but it is believed that the antibiotics stop the alcohol from being completely broken down and passed through the body, causing a build-up of acetaldehyde.


The reported effects have ranged from mild to very severe, but most may experience a "hangover-like" effect. Although most reactions have been mild to moderate, there has been a reported case of death from cardiovascular issues.


Cefotetan (Cefotan)

Cefotetan is related to cephalexin, as both are considered to be in the medication class called cephalosporins. However, cefotetan has a different chemical structure than other cephalosporins that is believed to be the reason for the interaction with alcohol. Alcohol should be used cautiously while on this medication, as the side effects of alcohol may be increased. Symptoms of flushing, changes in heart rate, and decreased blood pressure were reported in some people.


Sulfamethoxazole/trimethoprim (Bactrim)

Sulfamethoxazole/trimethoprim and alcohol can be used at the same time, but it should be noted that there have been a few cases where people have experienced increased side effects, such as flushing, nausea, palpitations, and trouble breathing.