Studies On The Pharmacodynamics And Pharmacokinetics Of Norfloxacin Hydrochloride In Silkworms

Norfioxacin-HCL is one of the fioroquinolones. In this paper , the pharmacokinetic characteristics of Norfloxacin-HCL following adding administration were conducted with healthy and B.sp. infected silkworms by using the (High performance liquid chromatography , HPLC) and microbiologic assay. The vitro activity of Norfloxacin-HCL against B.sp. and Bacillus thuringiensis and Serratia marcescena Bizio were determined by tube-test serial two fold dilution. The Pharmacodynamics of Norfloxacin-HCL on bacteria, infected silkworms were studied following adding administration.The inhibited experiment in vitro showed that the minimum inhibited concentration(MIC) of Norfloxacin-HCL , Enrofloxacin-HCL and Ciprofloxacin-HCL to B.sp is 0.78 ug/mL; The MIC to Bacillus thuringiensis is 0.19, 0.39, 0.39|ig/mL; The MIC to Serratia marcescena Bizio is 3.125 6.25, 1.5625 ug/mL.The data were analyzed with the pharmacokinetic computer program MCPKP. The pharmacokinetics showed that the concentration-time course of Norfloxacin-HCL in plasma following adding administration in healthy silkworms (25 mg/kg) can be described by one-compartment open model with first order absorption. The primary parameters were showen below: Ka 0.552?.007h'', Tmax 3.428?.008 h, Cmax 14.808?.645 ug-mL~', Ti/2Kei 1.778?.012 h; The concentration-time course of Norfloxacin-HCL in plasma following adding administration in infected silkworms(18 mg/kg) can be described by two-compartment open model with first order absorption. Compared with the primary parameters in healthy silkworms, the changement of primary parameters was showen below: the value Ka decreasesfrom 0.553 h'1 to 0.436 h'1, T,/2Ka increases from 1.252 h to 1.591 h, T|/2a decreases from 2.673 h to 1.981 h, Ti/2p decreases from 9.298 h to 5.338 h , Tmax decreases from 3.162 h to 3.019 h, AUC decreases from 81.194 mg/L-h to66.105mg/L-h.The results of pharmacokinetic investigation show that after Norfloxacin-HCL taking in healthy silkworms, it has many characteristics, for example, it can be absorbed quickly, the distribution is widespread, the precluding half time is short, the peak concentration is high, the time up to peak is short, and so on; The infection could affect the pharmacokinetic parameters. Compared with the healthy silkworms, the absorption is slower, the elimination and distribution increases , and the area under concentration-time curve decreases, the time up to peak shortens.According to the results of pharmacokinetics and pharmacodynamics, the reasonable administration project is suggested. On Bacillus thuringiensis infection the silkworms can be medicated via added to feed with the concentration of 250 ug/mL two times a day for two or three days; On Serratia marcescena Bizio infection the best medicated concentration is 500 fig/mL and feeds through out the day for one instar; On B.sp disease the medicated effect of rather low concentration (50 ug/mL) is hundred percent.