Cephalexin For Tooth Infection: Benefits & Side Effects

By Zina Semenovskaya, MD
Medically reviewed
September 7, 2021

Any toothache can be painful, but a tooth abscess, or infected tooth, is both painful and potentially risky.

Tooth infections commonly occur due to dental problems like cavities or gum disease. If left untreated, an abscessed tooth can result in more serious, even life-threatening health problems, including bacteria spreading to the face, bones, or bloodstream. 

To treat a tooth infection, a dentist or other healthcare provider may prescribe an antibiotic medication.

Antibiotics work by slowing or stopping the growth of bacteria, which in turn resolves the infection and the accompanying symptoms.

Cephalexin, also called Daxbia or Keflex, is one antibiotic for tooth infections. 

While cephalexin can be effective in treating some dental infections, it’s not without side effects and risks.

If your healthcare provider prescribes any antibiotic, including cephalexin, it’s important to follow their instructions throughout the treatment course.

And of course, if your infection isn’t resolving or your symptoms get worse, don’t hesitate to talk to your healthcare provider, dentist, or a K provider, who can help you figure out what’s going on. 

In this article, I’ll cover the benefits of taking cephalexin for a tooth infection, dose information for the drug, and how long it takes to work.

I’ll then outline some of the side effects of cephalexin, and tell you whether the drug is safe.

Benefits of Taking Cephalexin for a Tooth Infection 

When you have a bacterial infection, whether in your mouth or elsewhere in your body, your healthcare provider will probably prescribe an antibiotic medication to treat it.

Antibiotics work by blocking bacteria’s cell wall formation, which kills the germs and stops the infection and its symptoms. 

Cephalexin is in a class of antibiotics called cephalosporins.

While penicillin, amoxicillin, amoxicillin and clavulanate potassium (Augmentin), and clindamycin are the first-line antibiotic treatments for most dental infections, cephalexin may be considered when you have an allergy to those medications.

Cephalexin can be effective for treating dental abscesses and gum infections.

Along with tooth infections, cephalexin is sometimes used to treat skin infections and urinary tract infections, and after surgery.  

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Dosage information 

If your medical provider prescribes cephalexin, they’ll give you precise instructions for how and when to take the medication. 

Cephalexin is available in tablet, capsule, and suspension (liquid) form.

The dosage is based on your diagnosis, weight, and the severity of your condition. In children, cephalexin dosage is based on weight. 

The usual dosing for an adult with a tooth infection is a total of 1-4 grams of Cephalexin daily.

This dosage is taken in divided doses throughout the day. Providers usually write prescriptions as 250 milligrams four times a day, or 500 milligrams two to three times a day.

For more severe tooth infections, or tooth infections that have reached a person’s bones, a different antibiotic or dosing will likely be needed.

No matter how much cephalexin you are prescribed, try to take it at about the same time every day.

The medicine is best absorbed when taken on an empty stomach. It’s very important to take the whole course of antibiotics.

Don’t stop taking the medication when you start to feel better. Doing so can result in future infections that are harder to treat, or incomplete treatment of your current infection.

If you miss a dose of cephalexin, don’t double the dose to make up for it.

Instead, take your next dose as soon as you remember. If it’s too close to the time of your next dose, skip the one you missed. 

How Long Does It Take for Cephalexin to Work on a Tooth Infection? 

All medications take time to work. If you follow your provider’s instructions when taking cephalexin for a tooth infection, you can expect to start feeling better within a few days of starting the antibiotics.

If you aren’t improving after a few days, you’re experiencing severe side effects, or you’re starting to feel worse, seek medical advice from a healthcare provider or a K provider.

Potential Side Effects of Cephalexin

Cephalexin can be an effective way to resolve a tooth infection. But, like any medication, it can result in unwanted side effects.

Possible side effects of cephalexin may include: 

While there’s no need to adhere to a special diet for cephalexin, you may want to adjust your food routine if you experience stomach problems while taking this medication.

Yogurt and other probiotic-rich foods may help soothe antibiotic-related GI troubles.

If you’re taking cephalexin, avoid drinking alcohol.

Alcohol can increase side effects of this antibiotic medication, including nausea, drowsiness, and dizziness. 

Is Cephalexin Safe?

In general, cephalexin is considered a very safe medication, as long as it’s prescribed by a licensed medical professional and purchased from a pharmacy.

Cephalexin is also safest when you follow your provider’s instructions about how to take it. Never take more or less than prescribed.

Who shouldn’t take cephalexin?

Cephalexin is considered safe during pregnancy, but a provider may only prescribe it when absolutely necessary. Cephalexin is also considered safe for use while breastfeeding. 

Certain populations should not take cephalexin due to potential complications or drug interactions.

Let your healthcare provider know if you have any of the below conditions: 

  • Inflammation in the large intestine
  • Kidney disease with decreased kidney function
  • History of Clostridium difficile (C.diff) infection 
  • Liver disease

Don’t take cephalexin if you’re allergic to it or to other, similar antibiotics, known as cephalosporins.

Also, let your doctor know if you take the drugs metformin or probenecid, which can negatively interact with cephalexin. 

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Cephalexin risks

As with any drug, cephalexin comes with risks of an allergic reaction.

Some rare but serious reactions to cephalexin may include: 

  • Itching
  • Hives
  • Swelling in the face, throat, tongue, or lips 
  • Watery or bloody stool 
  • Fever
  • Wheezing
  • Hallucinations 

If you think you’re experiencing an allergic reaction to cephalexin, go to the emergency room or call 911.

And if you have unwanted or severe side effects that are not life threatening, don’t hesitate to reach out to your healthcare provider or a K provider, who can help treat them or find a new medication to treat your tooth infection. 

How K Health Can Help 

Did you know you can get affordable primary care with the K Health app?

Download K to check your symptoms, explore conditions and treatments, and if needed text with a provider in minutes. K Health’s AI-powered app is HIPAA compliant and based on 20 years of clinical data.

K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Zina Semenovskaya, MD

Dr. Semenovskaya specializes in emergency medicine, and received her medical degree from Weill Cornell Medical College. She is currently the medical director at Remote Emergency Medicine Consulting, LLC and splits her time working clinically as an emergency medicine attending in California and Alaska. She is the first of our doctors to be fluent in Russian.