[5] Cefalexin can treat certain bacterial infections, including those of the middle ear, bone and joint, skin, and urinary tract.

[4] Cefalexin is not effective against infections caused by methicillin-resistant Staphylococcus aureus (MRSA), most Enterococcus, or Pseudomonas.

[4] Like other antibiotics, cefalexin cannot treat viral infections, such as the flu, common cold or acute bronchitis.

For example, penicillin is the treatment of choice for respiratory tract infections caused by Streptococcus, but cefalexin may be used as an alternative in penicillin-intolerant patients.

[19] It is categorized in category A in Australia meaning that no evidence of harm has been found after being taken by many pregnant women.

[7] The most common adverse effects of cefalexin, like other oral cephalosporins, are gastrointestinal (stomach area) disturbances and hypersensitivity reactions.

[21] Signs and symptoms of an allergic reaction include rash, itching, swelling, trouble breathing, or red, blistered, swollen, or peeling skin.

[4][25] Histamine H2 receptor antagonists like cimetidine and ranitidine may reduce the efficacy of cefalexin by delaying its absorption and altering its antimicrobial pharmacodynamics.

[27] It is bactericidal and acts by inhibiting synthesis of the peptidoglycan layer of the bacterial cell wall.

[4] However, some bacterial cells have the enzyme β-lactamase, which hydrolyzes the β-lactam ring, rendering the drug inactive.

[26][31] The elimination half-life of cefalexin is approximately 30 to 60 minutes in people with normal renal function.

[14] The World Health Organization classifies cefalexin as highly important for human medicine.

[33] Brand names for cefalexin include Keflex, Acfex, Cephalex, Ceporex, L-Xahl, Medoxine, Ospexin, Torlasporin, Bio-Cef, Panixine DisperDose, and Novo-Lexin.