Keflex Patient Tips
Medically reviewed by C. Fookes, BPharm. Last updated on Nov 20, 2017.
How it works
- Keflex is a brand (trade) name for cephalexin. Cephalexin is an antibiotic that is used to treat infections caused by susceptible bacteria. Cephalexin is bactericidal (kills bacteria) and works in a similar way to penicillins. It binds to and blocks the activity of enzymes responsible for making peptidoglycan, an important component of the bacterial cell wall. Cephalexin is called a broad-spectrum antibiotic because it is effective against a wide range of bacteria.
- Keflex belongs to the class of antibiotics known as cephalosporins. Keflex is a first-generation cephalosporin and is mainly effective against gram-positive bacteria.
- Keflex treats a wide range of infections such as those occurring in the:
- Respiratory tract
- Genitourinary area
- and on the skin.
- Keflex has excellent activity against gram-positive staphylococci and streptococci bacteria, including susceptible isolates of: Staphylococcus aureus, Streptococcus pneumoniae, S. pyrogens, Haemophilus influenzae, Klebsiella pnumoniae, Moraxella catarrhalis, and Proteus mirabilis.
- May be given twice daily.
- May be given with or without food.
- Keflex is available as a generic under the name cephalexin.
If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:
- Diarrhea, dyspepsia, abdominal pain, nausea, have been reported. May alter some laboratory tests. Seizures have been reported rarely.
- Approximately 10% of people who are allergic to penicillin are also allergic to cephalosporins. Tell your doctor if you have ever had an allergy to antibiotics.
- The dosage of Keflex requires adjusting for people with moderate-to-severe kidney disease.
- Severe diarrhea, caused by overgrowth of a bacteria called Clostridium difficile, is a potential side effect of almost all antibacterial agents, including Keflex. Symptoms include persistent, watery and sometimes bloody diarrhea.
- May increase the time it takes for blood to clot. People with liver or kidney disease, who are malnourished, receiving a long course of therapy, or already on anticoagulants are more at risk.
- May interact with some drugs including metformin, probenecid, and some urinary glucose tests.
Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.
- Can be taken with or without food.
- Take exactly as directed and for the duration intended. Do not finish the course earlier than prescribed, even if you feel better because this encourages the growth of resistant bacteria. Do not take Keflex for any other infection other than the one you have been prescribed it for. Keflex will not treat viral infections such as the flu.
- Seek medical advice if chronic diarrhea develops during or following a course of Keflex.
- Talk to your doctor if you develop any worrying side effects after taking Keflex such as abdominal pain, excessive bruising or bleeding, or a rash.
Response and Effectiveness
- Peak concentrations of Keflex are reached one hour after dosing; however, it may take up to 48 hours before infection-related symptoms start to abate. Keep taking Keflex for the total duration prescribed, even if you feel better.
Keflex (cephalexin) [Package Insert]. Revised 04/2016. Pragma Pharmaceuticals, LLC https://www.drugs.com/pro/keflex.html
More about Keflex (cephalexin)
- Keflex Side Effects
- During Pregnancy or Breastfeeding
- Dosage Information
- Drug Images
- Drug Interactions
- Compare Alternatives
- Support Group
- Pricing & Coupons
- En Español
- 59 Reviews
- Generic Availability
- Drug class: first generation cephalosporins
- Keflex (Cephalexin Capsules and Tablets)
- Keflex (Cephalexin Suspension)
- Keflex (Advanced Reading)
Related treatment guides
- Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Keflex only for the indication prescribed.
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