Study on pharmacokinetic/pharmacodynamic model of amoxicillin against Staphylococcus aureus in serum and tissue fluid of pigs ex vivo.

【Objective】 The research was performed for the rational usage of amoxicillin in treating pigs infected by staphylococcus aureus. 【Method】 The combined method of pharmacokinetics in vivo and pharmacodynamics in vitro was used to survey and evaluate the pharmacokinetics-pharmacodynamics relationship of amoxicillin against staphylococcus aureus. 【Result】 The MICs of amoxicillin against Staphylococcus aureus in serum or tissue cage fluid were 0.2μg·mL-1MIC0.4μg·mL-1 in vitro. The concentration of amoxicillin that is more than MIC in serum or tissue fluid will be needed to inhibit the bacteria if lots of staphylococcus aureus was added. EC50 were 143.63±54.35 and 29.61±5.07 respectively in serum and tissue fluid of pigs after intramuscular administration at 10 mg·kg-1 body weight. Amoxicillin produced 50% of the maximal antibacterial effect when the concentration of amoxicillin was 2.39 μg·mL-1 and 0.49 μg·mL-1, respectively, in serum and tissue fluid. 【Conclusion】 Dosage regime should be designed according to specific case when amoxicillin was employed to treat pigs infected by staphylococcus aureus. I.M injections should be administered in the amount of 20mg daily per kilo of body weight, subdivided into injections every 12 hours when pigs are infected by low-grade infection of staphylococcus aureus. When the infection become more serious, dosage regime of 30-40mg daily per kilo body weight should be designed and subdivided into injections every 6-8 hours.