Cephalexin: 6 things you should know
Medically reviewed by C. Fookes, BPharm. Last updated on Jan 10, 2019.
1. How it works
- Cephalexin is an antibiotic that is used to treat infections caused by susceptible bacteria.
- Cephalexin belongs to the class of antibiotics known as cephalosporins.
- Cephalexin is a first-generation cephalosporin and is mainly effective against gram-positive bacteria.
- Cephalosporins are bactericidal (kill bacteria) and work in a similar way to penicillins. They bind to and block the activity of enzymes responsible for making peptidoglycan, an important component of the bacterial cell wall. They are called broad-spectrum antibiotics because they are effective against a wide range of bacteria.
- Treats a wide range of infections such as those occurring in the respiratory tract, ear, genitourinary area, bone, or on the skin.
- Cephalexin 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.
- Generic cephalexin is available.
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, and nausea are the most commonly reported. May alter some laboratory tests.Seizures have been reported rarely.
- About 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 cephalexin 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 cephalexin. 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 cephalexin for any other infection other than the one you have been prescribed it for. Cephalexin will not treat viral infections such as the flu.
- Seek medical advice if chronic diarrhea develops during or within a few months of finishing a course of cephalexin.
- Talk to your doctor if you develop any worrying side effects after taking cephalexin such as abdominal pain, excessive bruising or bleeding, or a rash.
6. Response and Effectiveness
- Peak concentrations of cephalexin are reached one hour after dosing; however, it may take up to 48 hours before infection-related symptoms start to abate.
Cephalexin capsules [Package Insert]. Revised 06/2018. Amella Pharma, LLC. https://www.drugs.com/pro/cephalexin.html
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use cephalexin only for the indication prescribed.
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- Drug class: first generation cephalosporins