Pharmacokinetics of two once-daily parenteral cephalexin formulations in dogs

Rebuelto, M., Montoya, L., Kreil, V., Ambros, L., Waxman, S., Albarellos G., Hallu, R. Pharmacokinetics of two once-daily parenteral cephalexin formulations in dogs. J. vet. Pharmacol. Therap.28, 419–423.

ABSTRACT

The aims of this study were to describe and compare the pharmacokinetic profiles and T_>MIC90 of two commercially available once-daily recommended cephalexin formulations in healthy adult dogs administered by the intramuscular (i.m.) route. Six beagle dogs received a 10 mg/kg dose of an 18% parenteral suspension of cephalexin of laboratory A (formulation A) and laboratory B (formulation B) 3 weeks apart. Blood samples were collected in predetermined times after drug administration. The main pharmacokinetic parameters were (mean ± SD): AUC_(0−∞), 72.44 ± 15.9 and 60.83 ± 13.2 μg·h/mL; C_max, 10.11 ± 1.5 and 8.50 ± 1.9 μg/mL; terminal half-life, 3.56 ± 1.5 and 2.57 ± 0.72 h and MRT_(0−∞), 5.86 ± 1.5 and 5.36 ± 1.2 h for formulations A and B, respectively. T_>MIC90 was 63.1 ± 14.7 and 62.1 ± 14.7% of the dosing interval for formulations A and B, respectively. Median (range) for t_max was 2.0 (2.0–3.0) h and 3.0 (2.0–4.0) for formulations A and B, respectively. Geometric mean ratios of natural log-transformed AUC_(0−∞) and C_max and their 90% confidence intervals (CI) were 0.84 (0.72–0.98) and 0.83 (0.64–1.07), respectively. The plasma profiles of cephalexin following the administration of both formulations were similar. No statistical differences between pharmacokinetic parameters or T_>MIC90 were observed, however, bioequivalence between both formulations could not be demonstrated, as lower 90% CI failed to fell within the selected range of 80–125% for bioequivalence.