Pharmacokinetics of CO.SMM sustained-release injection in buffaloes plasma

Blood samples were collected at different intervals after administration, and the concentrations of SMM and TMP in plasma were determined by high performance liquid chromatography (HPLC) and the pharmacokinetic program 3P97 was used to analyse the concentrations versus time data. The results revealed that the concentration-time data of SMM and TMP were respectively described by a one-compartment open model with first-order absorption and two-compartment open model with first-order absorption after single intramuscular administration of CO.SMM sustained-release injection, and the main pharmacokinetic parameters of SMM and TMP in CO.SMM sustained-release injection were as follows: t1/2Ka 0.41 h,t1/2β 11.46 h,AUC 1 107 h·μg·mL-1,Vd 0.75 L·kg-1,CLB 0.05 L·kg-1·h-1,tmax 2.03 h,Cmax 59.24 μg·mL-1,and t1/2Ka 0.47 h,t1/2β 3.25 h,AUC 261.18 h·μg·mL-1,Vd 0.89 L·kg-1,CLB 0.19 L·kg-1·h-1,tmax 1.02 h,Cmax 76.85 μg·mL-1, and the concentration-time data of SMM was described by two-compartment open model with first-order absorption after single intramuscular administration of SMM and the main pharmacokinetic parameters were as follows: t1/2K 0.47 h,t1/2β 3.25 h,AUC 261.18 h·μg·mL-1,Vd 0.89 L·kg-1,CLB 0.19 L·kg-1·h-1,tmax 1.02 h,Cmax 76.85 μg·mL-1, which indicated that the absorption half-life of SMM in the two preparations had no significant difference(P0.05), but the elimination half-life and peak time of SMM in CO.SMM sustained-release injection were significantly longer than SMM injection(P0.01), and the Cmax of the latter was significantly higher than the former(P0.01), so in vivo SMM released slowly, delayed the time of peaking, elimited slowly and sustained the blood drug level after intramuscular administration of CO.SMM. All these demonstrated that CO.SMM sustained-release injection has the sustained-release-long-acting property.