cefaleksiin

Cephalexin (cefaleksiin in some languages) is a first-generation cephalosporin antibiotic used to treat a range of bacterial infections. It works by inhibiting bacterial cell wall synthesis through binding to penicillin-binding proteins, thereby blocking transpeptidation and weakening the wall.

Its antimicrobial spectrum covers many gram-positive cocci, including Streptococcus species and penicillin-susceptible Staphylococcus aureus, and some gram-negative organisms such as Escherichia coli, Klebsiella spp., and Proteus mirabilis. It has limited activity against Enterococcus and anaerobes; it is not effective against methicillin-resistant Staphylococcus aureus (MRSA) or most beta-lactamase–producing strains.

Common indications include skin and soft tissue infections, otitis media, streptococcal pharyngitis, and uncomplicated urinary tract infections. It is also used for dental infections and certain other mild to moderate infections where susceptible organisms are suspected.

Pharmacokinetics: orally administered, well absorbed, with peak plasma levels within about 1 hour. It distributes into most body fluids and tissues and is primarily excreted by the kidneys. The half-life is roughly 1 hour in individuals with normal renal function, and dosing must be adjusted in renal impairment.

Dosing varies by infection and patient factors; typical adults receive 250–500 mg every 6 hours, and pediatric dosing is about 25–50 mg/kg/day in divided doses. Common adverse effects include gastrointestinal upset, rash, and hypersensitivity reactions. Prolonged use or broad exposure can lead to superinfections and Clostridioides difficile infection. Contraindications include known allergy to cephalexin or other cephalosporins; caution is advised in patients with penicillin allergy. Interactions include probenecid and antacids that can alter absorption. Cephalexin is generally considered compatible with pregnancy and is excreted in breast milk.