Brand Name:Ceporex, Keflex, Novo-Lexin, Nu-Cephalex, PMS-Cephalexin

Prescription needed: Yes

What is this drug used for?

Cephalexin is a cephalosporin antibiotic that is used in the treatment of sinus infections, ear infections, throat infections, pneumonia, urinary infections, bone infections, skin and soft tissue infections. May be used as a preventative treatment prior to dental procedures.

Is there any reason not to take this drug?

Do not take this medication if you are allergic to cephalexin or any other cephalosporins, or if you have ever had a serious allergic reaction to other beta lactam antibiotics such as penicillin, amoxicillin, cloxacillin or ampicillin. Tell your doctor specifically if you have or have ever had:

  • bleeding problems
  • colitis or serious inflammation of your digestive system
  • kidney or liver disease

What about possible side effects?

This medication is usually well tolerated but you should be aware of some potential side effects. The following side effects are more common and can be quite bothersome, but unless they are severe, you should continue taking cephalexin as prescribed. Contact your doctor or pharmacist to get advice on how to manage these side effects.

More common side effects include:

  • diarrhea
  • nausea
  • vomiting
  • abdominal pain or discomfort
Less common side effects include:

  • headaches
  • dizziness
  • mild skin rash
  • fever
  • abnormal liver tests
  • vaginitis
Antibiotics may make you prone to oral thrush infections and vaginal yeast infections. Contact your doctor or pharmacist regarding treatments.

These side effects may be related to the dose, the use of other medications and other factors (e.g. older age, other medical conditions).  As well, some of these side effects may go away with time. Talk to your doctor or pharmacist about whether you have any risk factors that may make you more sensitive to these side effects.  Contact your doctor if these symptoms continue or become worse.

Call your doctor immediately if you experience any of the following more serious side effects:

  • difficulty breathing or swallowing
  • severe dizziness
  • severe headache
  • hives all over the body or near the face and throat
  • itching all over the body
  • seizures
  • severe skin rash
  • swelling of the lips, face or tongue
  • unusual bleeding or bruising
  • wheezing
  • blood in the stool
This is not a complete list of side effects. If you are concerned about these or other unusual symptoms while taking this medication, ask your doctor and/or pharmacist for more information and advice.

What if I am taking other drugs?

Always provide your doctor with a list of all other drugs you are taking (including over-the-counter medications and herbal/natural products) as they may interact with and/or may change the safety or effectiveness of either drug. Tell your doctor specifically if you are taking any of these drugs as he/she may need to make changes or monitor you more closely:

  • Aminoglycoside antibiotics which are given intravenously (e.g. tobramycin, gentamicin, amikacin) – may increase risk of kidney problems
  • Probenecid - increased chances of side effects from cephalexin but may be used to improve how well cephalexin treats your infection
  • typhoid vaccine e.g. Vivotif – wait at least 24 hours after stopping ampicillin to vaccinate with the oral typhoid vaccine
  • birth control pills – there have been case reports suggesting antibiotics may decrease how well your birth control pills work to prevent pregnancy. While this interaction is unlikely, for peace of mind, consider using an additional method of birth control (i.e. condom) for the rest of that cycle
  • Vancomycin – may increase risk of kidney problems
This is not a complete list of drug interactions. Ask your doctor or pharmacist to review your list of medications.

Other information:

Special instructions: If you have diabetes and regularly check your urine for sugar using Clinitest tablets, cephalexin may contribute to incorrect results

If you experience diarrhea or vomiting, it is important to drink plenty of fluids (juices, Gatorade, Gastrolyte, Pedialyte in children) to prevent dehydration.

Dietary precautions: Cephalexin may cause stomach upset, nausea or diarrhea. Taking cephalexin with food, a meal or milk may minimize these side effects.

Some of the stomach-related side effects may be minimized if you add some yoghurt or buttermilk to your diet while on a course of cephalexin.

Children: Safely used in appropriate doses.

Seniors: Safely used in appropriate doses.

Pregnant women: The cephalosporin group of antibiotics is generally accepted as safe for use in pregnancy. Failing to treat your infection may pose a greater risk to your unborn child. Consult with your doctor if you have questions.

Women who are nursing: Cephalexin passes into breast milk in low concentrations and is considered safe for use in nursing women. Your infant may experience diarrhea or mild skin rash. Just like adults have the risk of an allergic reaction, there is also the risk of an allergic reaction in your infant

People who drive or operate machinery: Safely used

Alcohol: No specific problems with alcohol consumption. Always drink in moderation.

Overdose: Taking a large dose of cephalexin may cause nausea, stomach upset and diarrhea. If you experience any unusual reactions or if you seriously exceed the recommended dosage, call your doctor or 911.

Stopping the drug:  In order to clear up your infection completely, you must take cephalexin for the entire prescribed course of treatment even if you feel better.

If you miss a dose:  Take any missed dose as soon as possible, then continue as prescribed on your medication bottle. Taking cephalexin around the clock as prescribed will ensure optimal effect. Do not take a double dose to make up for a missed dose.

Storage conditions: Store as directed on packaging, particularly if you have the cephalexin liquid suspension which should be kept in the refrigerator. Do not freeze. Otherwise, store in a closed container; cool (below 25C), dry location away from excess moisture (not in the bathroom); direct light, always out of reach of children.