The Population Pharmacokinetics of Imipenem in Patients With Ventilator-associated Pneumonia

This is prospective, randomized and crossover design to assess the pharmacokinetic and pharmacodynamics of three regimen. * 0.5-hr infusion of imipenem 0.5 g every 6 hrs * 2-hr infusion of imipenem 0.5 g every 6 hrs * 2-hr infusion of imipenem 1 g every 6 hrs Clinical and laboratory data such as Age,Sex, Body weight, CBC, Electrolyte, Vital signs, APACHE II score, BUN, Cr, Sample and Blood culture will be collected. Nine patients will be enrolled in this study. After completion of the imipenem therapy for 3 days in this study, all patients will receive other sensitive antibiotics to eradicate their bacterial infections. Blood samples (approximately 3 ml) will be obtained by direct venepuncture at the following time: 0, 0.5, 1, 2, 3, 4, 5 and 6 after 4th dose of imipenem. Concentration of imipenem in plasma will be measured by HPLC method. Then, the data will be simulated in Monte Carlo technique (Computer model) to get PK/PD index (40%T\>MIC) and reported to % PTA (Probability Target Attainment) and %CFR (Cumulative Faction Response).