Variable absorption of clavulanic acid after an oral dose of 25 mg/kg of Clavubactin® and Synulox® in healthy dogs

The aims of this investigation were to calculate the pharmacokinetic parameters and to identify parameters, based on individual plasma concentration–time curves of amoxicillin and clavulanic acid in dogs, that may govern the observed differences in absorption of both drugs. The evaluation was based on the data from plasma concentration–time curves obtained following a single dose in an open, randomized, two‐way crossover study involving 24 male Beagle dogs treated with two Amoxi–Clav formulations (A Clavubactin ® and B Synulox ® , each with 200/50 mg). Plasma amoxicillin and clavulanic acid concentrations were determined using validated bioassay methods. The half‐life of elimination of amoxicillin was 1.5 h ( t 1/2 = 1.52 ± 0.19 h, C max = 11.4 ± 2.74 μg/mL), and that of clavulanic acid 0.76 h ( t 1/2 = 0.71 ± 0.23 h, C max = 2.06 ± 1.05 μg/mL). There was a fivefold variation in the AUC t of clavulanic acid for both formulations, while the AUC t of amoxicillin varied by a factor of 2. The mean ratio of the AUC t amoxicillin : clavulanic acid was 12.7 ± 3.65 for formulation A and 11.8 ± 5.22 for formulation B ( P = 0.51).