Cephalexin

Cephalexin is a first-generation cephalosporin antibiotic, a beta-lactam that inhibits bacterial cell wall synthesis by binding penicillin-binding proteins. It primarily covers many Gram-positive cocci and some Gram-negative rods, but has limited activity against MRSA and anaerobes; resistance can occur.

Indications: used for mild to moderate infections caused by susceptible organisms, including skin and soft tissue infections (cellulitis, impetigo), otitis media, sinusitis, pharyngitis/tonsillitis, and certain uncomplicated urinary tract infections.

Administration and dosing: available as capsules and oral suspension. Typical regimens vary by infection and patient, commonly 250 mg to 500 mg every 6 hours or 500 mg every 12 hours, for 7–14 days. Take with or without food; finish prescribed course.

Safety and contraindications: common adverse effects include gastrointestinal upset, diarrhea, nausea, rash. Hypersensitivity reactions can occur; severe penicillin or cephalosporin allergy is a contraindication. Caution in kidney impairment; dose adjustment may be necessary. Cross-reactivity with penicillins exists but is lower with first-generation agents.

Pharmacokinetics and interactions: rapidly absorbed after oral administration and eliminated mainly by the kidneys; half-life about 1 hour in people with normal kidney function. Probenecid can raise cephalexin levels by reducing renal excretion. Use with caution with anticoagulants in some patients.

Brand and history: Cephalexin is a first-generation cephalosporin marketed under names such as Keflex; widely prescribed for oral therapy.