Prescribing-label excerpts
Cephalexin
Reference for: Cephalexin. Source presentation: capsule. Source route: oral.
The cited studies use standard-release capsule. The catalogue entry has a different or unspecified release description; these study values do not establish its absorption profile.
Mechanism of action
Cephalexin is a cephalosporin antibacterial drug [see Microbiology (12.4)].
Pharmacokinetics
Absorption — Cephalexin is acid stable and may be given without regard to meals. Following doses of 250 mg, 500 mg, and 1 g, average peak serum levels of approximately 9, 18, and 32 mcg/mL, respectively, were obtained at 1 hour. Serum levels were detectable 6 hours after administration (at a level of detection of 0.2 mcg/mL).
Distribution — Cephalexin is approximately 10% to 15% bound to plasma proteins.
Excretion — Cephalexin is excreted in the urine by glomerular filtration and tubular secretion. Studies showed that over 90% of the drug was excreted unchanged in the urine within 8 hours. During this period, peak urine concentrations following the 250 mg, 500 mg, and 1 g doses were approximately 1000, 2200, and 5000 mcg/mL respectively.
Drug Interactions — In healthy subjects given single 500 mg doses of cephalexin and metformin, plasma metformin mean Cmax and AUC increased by an average of 34% and 24%, respectively, and metformin mean renal clearance decreased by 14%. No information is available about the interaction of cephalexin and metformin following multiple doses of either drug.
Selected passages from the cited U.S. prescribing label. The studies concern the source product and populations named in each passage; they do not establish Walter-product bioequivalence, an approved indication, or the kinetics of another fixed combination. Tables and the full prescribing information remain available in the source.
Source: DailyMed: Cephalexin — capsule
Reference accessed . Label revision: 2026-08-24.
