Pharmacokinetics and Pharmacodynamics of a Novel Amoxicillin/Sulbactam/Prednisolone Intramammary Infusion in Lactating Cows after Repeated Administrations

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A novel anti-mastitis preparation, amoxicillin/sulbactam/prednisolone intramammary infusion (CAIMM), containing 200 mg amoxicillin, 50 mg sulbactam and 10 mg prednisolone per 3 g formulation, was developed, and corresponding pharmacokinetic was conducted in healthy lactating cows after repeated administrations. The combination product was a white- to cream-colored oil suspension which had perfect syringeability and flowability, according to the Technical Standards set by the Ministry of Agriculture of People's Republic of China. The concentrations of drugs in quarter milk were determined by ultra-high performance liquid chromatography tandem mass spectrometric (UPLC-MS/MS) method. No significant difference in the major PK parameters (Cmax, Tmax, MRT, t1/2λ and AUClast) was observed when the parallel study was performed using the available combination product (Synulox® LC) from Pfizer with the aim to compare the two formulations. The MIC90 determined in 106 Staphylococcus spp., 64 Streptococcus spp. and 18 Escherichia coli isolated strains was 0.5, 0.25 and 2 µg/ml, respectively. To study the efficacy of CAIMM to treat bovine clinical mastitis, the pharmacokinetic/pharmacodynamic (PK/PD) evaluation showed that the effective duration of action (t>MIC90) for CAIMM (42 ± 2.46 hr) was increased by 0.86 times compared with Synulox® LC (34 ± 3.17 hr), but the difference was not significant (P>0.05).