Pharmacokinetics Of20%Doxycycline Hydrochloride Injection In Pigs

The pharmacokinetics of20%doxycycline hydrochloride injection were studied in young pigs following single intramuscular (10and20mg/kg b.w.) and intravenous (10mg/kg b.w.) administration of doxycycline hydrochloride injection. Eighteen pigs were used in pharmacokinetics study, and randomly divided into three groups. Blood samples were obtained at different time intervals after administration respectively. The concentration of doxycycline in plasma were determined by reverse high performance liquid chromatography (HPLC). The concentration-time date of doxycycline in plasma were analysed with3p87compute program.The concentration-time date of doxycycline in plasma fitted to a two-compartment open model with zero-order absorption after single intravenous (10mg/kg b.w.) administration in pigs. The main pharmacokinetic parameters were as follows: ti/2p:(5.84±1.28) h, CL(S):(0.16±0.02)1/kg/h, AUC:(62.39±9.28) μg/mL·h。The concentration-time date of doxycycline in plasma fitted to a two-compartment open model with first-order absorption after single intramuscular (10mg/kg b.w.) administration in pigs. The main pharmacokinetic parameters of doxycycline were as follows:t1/2ka:(0.09±0.02)h, t1/2p:(12.56±2.43) h, Tmax:(0.46±0.08) h, Cmax:(4.00±0.77) μg/mL, AUC:(27.59±2.56)mg/l·h, F:44.22%.The concentration-time date of doxycycline in plasma fitted to a two-compartment open model with first-order absorption after single intramuscular (20mg/kg b.w.) administration in pigs. The main pharmacokinetic parameters were as follows: t1/2ka:(0.11±0.04)h, t1/2β:(16.60±1.66) h, Tmax:(0.52±0.10) h, Cmax:(6.51±0.53) μg/mL, AUC:(50.12±6.33) mg/1·h, F:40.17%.The above results showed that the20%doxycycline hydrochloride injection absorbed rapidly, distributed widely and have a low bioavailability after single intramuscular administration in pigs. There were significant differences in Cmax, AUC, t1/2β and there were no significant differences in t1/2ka, tmax with the increase of doses. The doxycycline hydrochloride injection could be injected at the dose of20mg/kg b.w. once a day or at the dose of20mg/kg b.w. every other day in the treatment of infectious diseases caused by sensitive bacterial in pigs.