Abstract:

The pharmacokinetics of cephalexin, a first generation cephalosporin, were investigated in dogs using two formulations marketed for humans, but also often employed by practitioners for pet therapy. Cephalexin was administered to five dogs intravenously and intramuscularly as a sodium salt and by the oral route as a monohydrate. The dosage was always 20 mg/kg of active ingredient. A microbiological assay with Sarcina lutea as the test organism was adopted to measure cephalexin concentrations in serum.

The mean residence time (MRT) median values after intravenous (i.v.), intramuscular (i.m.) and oral administration (p.o.) were 86 min, 200 min, and 279 min, respectively.

After i.m. and oral dosing the peak serum concentrations (24.2 ± 1.8 μg/mL and 20.3 ± 1.7 μg/mL, respectively) were attained at 90 min in all dogs and bioavailabilities were 63 ± 10% and 57 ± 5%, respectively.

The time course of the cephalexin serum concentrations after oral administration was best described by a model incorporating saturable absorption kinetics of the Michaelis-Menten type; thus in the gastrointestinal tract of dogs a carrier mediated transport for cephalexin similar to that reported in humans, may exist.

The predicted average serum concentrations of cephalexin after repeated i.m and oral administration indicated that, in order to maintain the therapeutic concentrations, the 20 mg/kg b.w. dosage should be administered every 6-8 h.

Document Type: Research article

DOI: 10.1046/j.1365-2885.1999.00208.x

Affiliations: 1: Istituto di Farmacologia e Tossicologia Veterinaria, Facoltà di Medicina Veterinaria, Via Celoria 10, 20133 Milano, Italy., 2: Pubblica Veterinaria e Patologia Animale, Via Tolara di Sopra 50, 40064 Ozzano, Emilia (B0), Italy., 3: Dipartimento di Morfofisiologia Veterinaria e Produzioni Animali, Via Tolara di Sopra 50, 40064 Ozzano Emilia (B0), Italy., 4: Istituto di Patologia Speciale e Clinica Medica Veterinaria, Facoltà di Medicina Veterinaria, Viale delle Piagge, 256124 Pisa, Italy., 5: Istituto di Patologia Animale e Igiene Veterinaria, Facoltà di Medicina Veterinaria, Agripolis, 35020 Legnaro (PD), Italy.