title: Pharmacodynamic modeling of beta-lactam antibiotics for the empiric treatment of secondary peritonitis: a report from the OPTAMA program.
abstract: BACKGROUND
  In this report of the OPTAMA (Optimizing Pharmacodynamic Target Attainment using the MYSTIC Antibiogram) program, we utilized Monte Carlo simulation to compare the probabilities of achieving bactericidal time above the minimum inhibitory concentration (MIC) (%T > MIC) exposures for imipenem-cilastatin 500 mg q6h and 1000 mg q8h, meropenem 500 mg q6h and 1000 mg q8h and piperacillin/tazobactam 3.375 g q6h and 4.5 g q8h in the empiric treatment of secondary peritonitis.
  
  
  METHODS
  The prevalence of pathogens causing secondary peritonitis was identified from the primary surgical and infectious diseases literature. Data for these pathogens with respect to MIC were obtained from the 2003 MYSTIC surveillance study and weighted by the prevalence of each pathogen. A sensitivity analysis varying the prevalence of P. aeruginosa was performed with two additional models to determine the robustness of the data. Pharmacokinetic parameters, obtained from previously published studies in healthy volunteers were used to simulate the %T > MIC for 10,000 patients receiving imipenem-cilastatin, meropenem, and piperacillin/tazobactam. The likelihood of obtaining bactericidal exposure is reported.
  
  
  RESULTS
  Empiric utilization of imipenem-cilastatin and meropenem 500 mg q6h and 1000 mg q8h regimens achieved 99.6%-99.7% likelihood of bactericidal exposure. Piperacillin/ tazobactam 3.375 g q6h and 4.5 g q8h produced bactericidal target attainments of 92.9% and 85.2%, respectively. Models simulating higher prevalence of P. aeruginosa reduced the likelihood of bactericidal exposure for piperacillin/tazobactam regimens significantly and had little effect on the carbapenems.
  
  
  CONCLUSIONS
  All of the beta-lactams used in the current analysis were predicted to achieve high target attainment consistently for the empiric treatment of secondary peritonitis. However, imipenem-cilastatin 500 mg q6h and 1000 mg q8h, meropenem 1000 mg q8h and 500 mg q6h, and piperacillin/tazobactam 3.375 g q6h achieved the highest likelihood. These, in particular, would be effective choices for the empiric treatment of secondary peritonitis.
authors.affiliation: Center for Anti-Infective Research and Development, Hartford Hospital, Hartford, Connecticut 06102, USA.
authors.forename: Srividya
authors.initials: S
authors.lastname: Kotapati
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Kuti
authors.forename: David P
authors.initials: DP
authors.lastname: Nicolau
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000493:pharmacokinetics; D015377:Cilastatin / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology; D000077728:Cilastatin, Imipenem Drug Combination; D004338:Drug Combinations; D006801:Humans; D015378:Imipenem / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology; D000077731:Meropenem; D008826:Microbial Sensitivity Tests; D008954:Models, Biological; D009010:Monte Carlo Method; D010397:Penicillanic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000493:pharmacokinetics / Q000494:pharmacology; D010538:Peritonitis / Q000188:drug therapy* / Q000382:microbiology; D010878:Piperacillin / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology; D000077725:Piperacillin, Tazobactam Drug Combination; D011552:Pseudomonas Infections / Q000188:drug therapy / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D013845:Thienamycins / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology; D047090:beta-Lactams / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D004338:Drug Combinations; D013845:Thienamycins; D047090:beta-Lactams; D015377:Cilastatin; D000077725:Piperacillin, Tazobactam Drug Combination; D015378:Imipenem; D010397:Penicillanic Acid; D000077728:Cilastatin, Imipenem Drug Combination; D000077731:Meropenem; D010878:Piperacillin