左氧氟沙星药代动力学/药效学研究

目的评价左氧氟沙星的治疗方案。方法给12名健康志愿者单剂静脉滴注200、300和500mg左氧氟沙星后测定其血、尿药物浓度,计算药代动力学(PK)参数。体外药效学(PD)研究系测定左氧氟沙星对近期823株临床分离菌的药敏参数最低抑菌浓度(MIC)],并与其他相关抗菌药进行比较。根据上述研究结果计算左氧氟沙星血药峰浓度(Cmax)/MIC和血药浓度时间曲线下面积(AUC)/MIC的PK/PD参数,据此推荐左氧氟沙星用于不同病原菌感染的治疗方案。结果临床PK研究结果显示单剂静脉滴注左氧氟沙星200、300和500mg后,Cmax分别为3.4mg/L±0.8mg/L、4.8mg/L±1.4mg/L和7.6mg/L±1.1mg/L,AUC0∞分别为14.4mg·h/L±2.5mg·h/L、21.9mg·h/L±4.5mg·h/L和38.3mg·h/L±4.9mg·h/L,消除半衰期(T1/2β)分别为6.2h±0.4h、6.4h±0.9h和6.5h±0.6h,给药后24h内自尿中累积排出给药量的69%±5%、69%±6%和65%±4%。体外PD研究结果显示左氧氟沙星对溶血性链球菌、卡他莫拉菌具有高度抗菌活性,对肺炎链球菌(包括青霉素不敏感株)、流感嗜血杆菌、甲氧西林敏感金葡菌、肺炎克雷伯菌、嗜麦芽窄食单胞菌具有良好抗菌作用,对铜绿假单胞菌、肺炎克雷伯菌亦具有较好抗菌作用,甲氧西林耐药金葡菌(MRSA)、肠球菌则对左氧氟沙星大多呈现耐药,而大肠埃希菌则半数以上对其呈现耐药。PK/PD参数计算结果显示以1次/d给药方案为宜。左氧氟沙星每日200mg治疗卡他莫拉菌感染预期可获良好效果,每日300mg治疗溶血性链球菌感染预期有效。治疗肺炎链球菌、流感嗜血杆菌所致呼吸道感染则需每日500mg预期可达良好疗效,而治疗对该药呈现敏感的肺炎克雷伯菌、大肠埃希菌、铜绿假单胞菌、嗜麦芽窄食单胞菌所致呼吸道、尿路感染则至少每日500mg,而对MRSA、肠球菌感染,PK/PD参数预示疗效不佳。结论以PK/PD原理制定的左氧氟沙星给药方案用于临床可望获得良好的疗效。

Study of pharmacokinetics/pharmacodynamics of levofloxacin

OBJECTIVE: To evaluate the dosing regimens of levofloxacin. METHODS: The drug concentrations in serum and urine were assayed by HPLC method and the pharmacokinetic parameters were calculated after intravenous infusion of a single dose of 200 mg, 300 mg and 500 mg levofloxacin to healthy volunteers. The in vitro activity MIC of levofloxacin against 823 clinical isolates were determined and compared with other antimicrobial agents. Based on the above results, the PK/PD parameters C(max)/MIC and AUC/MIC were calculated and the dosing regimens of levofloxacin were proposed for infections caused by different pathogens. RESULTS: The results of clinical pharmacokinetic study showed that the C(max) of levofloxacin was 3.4 mg/L +/- 0.8 mg/L, 4.8 mg/L +/- 1.4 mg/L and 7.6 mg/L +/- 1.1 mg/L respectively, AUC(0-infinity) was 14.4 mg.h/L +/- 2.5 mg.h/L, 21.9 mg.h/L +/- 4.5 mg.h/L and 38.3 mg.h/L +/- 4.9 mg.h/L respectively, T(1)/2beta was 6.2 h +/- 0.4 h, 6.4 h +/- 0.9 h and 6.5 h +/- 0.6 h respectively, and 69% +/- 5%, 69% +/- 6%, and 65% +/- 4% of the doses were excreted in urine within 24 h after intravenous infusion of a single dose of levofloxacin 200 mg, 300 mg and 500 mg. The in vitro pharmacodynamic study showed that levofloxacin was highly active against Hemolytic streptococcus and Mcraxella catarrhalis. It was active against Streptococcus pneumoniae (including penicillin nonsusceptible strains), Hemophilns influenzae, methicillin-sensitive Staphylococcus aureus (MSSA), Klebsiella pneumoniae and Stenotrophomonas maltophilia. Levofloxacin also had good activity against Pseadomonas aeruginosa and K.pneumoniae. However, most of isolates of interococcal spp. were resistant to levofloxacin. Above 50% of Escherichia coli isolates were resistant to levofloxacin. Based on the results of PK/PD parameters, the adequate dosing regimens of levofloxacin should be once daily 200 mg once daily of levofloxacin was expected to be effective for the treatment of infections caused by M. catarrhalis. The regimen of 300 mg once daily could be effective for the treatment of infections caused by Hemolytic streptococcus. 500 mg once daily of levofloxacin was expected to be effective for the treatment of respiratory tract infections caused by S. pneumoniae or H. influenzae. For treatment of respiratory tract infections and urinary tract infections caused by levofloxacin-susceptible organisms including K. pneumoniae, E. coli, P. aeruginosa, and S.maltophilia, 500 mg once daily of levofloxacin was needed to obtain good clinical efficacy. But PK/PD parameters predicted that 500 mg daily of levofloxacin was not effective for infections caused by methicillin-resistant Staphylococcus aureus (MRSA) and Enterococci. CONCLUSION: The proposed dosing regimens of levofloxacin based on PK/PD concepts are expected to provide good efficacy in clinical practice.