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As is true for any other medication, there may be some instances where cephalexin use is not recommended or usage will have to be adjusted in order to prevent or reduce the risk of negative interactions occurring from other drugs, medical conditions, or even food and drink.

NOTE: Many interactions listed on this page should not necessarily stop you from taking this antibiotic. Always follow to your physicians instructions, but if you have a concern or want to discuss one of these interactions don’t hesitate to ask your physician.

Drug Interactions

According to the FDA, drugs that may interact with cephalexin include the following:

  • Metformin (Glucophage, Glumetza, Riomet)
  • Probenecid (reduces uric acid)
  • Blood thinners [e.g., warfarin (Jantoven, Coumadin)]
  • Vaccines that contain live bacteria, including BCG (Bacille Calmette-Guérin, a tuberculosis vaccine) and typhoid vaccines
  • Prescription and over-the-counter medicines, vitamins, and herbal supplements

Please note that this list may not be complete, and other interactions with drugs not listed here may occur. Before taking any drug, a person should talk to their health care provider about all the medicines and supplements they currently use. 

Cephalexin and Birth Control

It’s unlikely that cephalexin interacts with hormonal birth control in most people, although it’s not known for certain. Some other classes of antibiotics, like rifamycin, are known to affect a woman’s hormones and may reduce the effectiveness of oral contraceptives. This can increase the chance of pregnancy.

Even though research suggests cephalexin isn’t likely to interact with hormonal birth control, many doctors suggest using back-up birth control methods while taking the antibiotic as a precaution. You can learn more about non-hormonal birth control options by visiting our page on the subject.

Cephalexin and Tylenol

There have been no reported interactions between cephalexin and Tylenol (acetaminophen, Paracetamol), but this fact does not mean interactions aren’t possible. 

Cephalexin and Ibuprofen

There also have been no reported interactions between cephalexin and ibuprofen (Advil, Motrin IB, NeoProfen). Again, this fact does not necessarily mean drug interactions aren’t possible. Anyone who may take cephalexin should let their doctor know about all prescription and over-the-counter medications they’re taking.

Cephalexin and Penicillin

Cephalexin and penicillin belong to two different classes of antibiotics. No interactions have been reported between the two drugs.

Food Interactions

Overall, the body absorbs this drug more rapidly if patients take it on an empty stomach. Some doctors, though, advise taking it with food to reduce the risk of stomach upset. However, sometimes the foods we eat and the beverages we drink can also interact with our medications. Food and drink that could possibly interact with cephalexin in some people include:

  • Alcohol
  • Grapefruit (not certain, but grapefruit and grapefruit juice can negatively interact with many other drugs, including other types of antibiotics)
  • Carbonated beverages
  • Chocolate
  • Tomato-based products
  • Foods or supplements containing zinc 

Please note that this list may not be complete, and there may be other foods and beverages that interact with this drug.

Cephalexin and Alcohol

For more information, please visit our page on cephalexin and alcohol interactions.

Cephalexin and Dairy

This does NOT pertain to cephalexin, however, only other types of antibiotics and medications.Dairy products are often high in calcium, which can interfere with the body’s ability to absorb certain types of antibiotics, such as quinolones. So, some doctors may advise people to avoid consuming dairy or other products fortified with calcium when taking this medication.

Disease & Conditions Interactions

Sometimes certain medications can increase the risk of negative side effects for patients with certain diseases or other medical conditions. According to the FDA, diseases and medical conditions that are known to negatively interact with cephalexin include:

  • Liver diseases
  • Kidney diseases
  • Conditions affecting the colon or gastrointestinal (GI) tract
  • Heart disease
  • Seizure conditions

Please note that this list may not be complete, and there may be other diseases and medical conditions where patients should not take this drug.

Cephalexin and Anxiety

According to Mayo Clinic, cephalexin may cause anxiety in some people, although the incidence of this occurrence is not known. For individuals already living with an anxiety-related disorder, this medication may make their symptoms more pronounced.

Cephalexin and Breastfeeding

Cephalexin is considered safe for breastfeeding people to use. Some research suggests that maternal oral doses of up to 1 gram of cephalexin leads to peak levels in breast milk about 4 to 5 hours after dosage. However, even the peak level is low enough that experts do not think it is likely to cause problems for breastfeeding infants. Still, some doctors recommend that cephalexin should be used with caution or stopped while breastfeeding.

Cephalexin and Pregnancy

For more information, please visit our page on cephalexin and pregnancy risks.

Cephalexin and Penicillin Allergy

Cephalexin and penicillin are two distinct classes of antibiotics, although they work in similar ways. Historically, experts suggest that about 10 percent of people with a penicillin allergy are also allergic to cephalexin, but this speculation isn’t fully conclusive, given current research. That said, anyone with an allergy to any type of medication, including penicillin, should speak to their doctor about it before taking cephalexin. 

Other Interactions

Other potential interactions include the following.

Cephalexin and Sun

Cephalexin may make a person’s skin more sensitive to the sun, which can increase a person’s risk for sunburn. People taking this medication should be careful to use sunscreen and avoid excessive sunlight exposure.

NOTE: Many interactions listed on this page should not necessarily stop you from taking this antibiotic. Always follow to your physicians instructions, but if you have a concern or want to discuss one of these interactions don’t hesitate to ask your physician.

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.


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