Cost efficacy of tazobactam/piperacillin versus imipenem/cilastatin in the treatment of intra-abdominal infection

Objective: To compare the cost, efficacy and cost efficacy of tazobactam/piperacillin and imipenem/cilastatin in the treatment of intra-abdominal infection. Design: The analysis was retrospective and based on a decision tree. Effectiveness data were obtained from 19 published clinical trials. Direct costs were quantified per patient from the time the decision was made to administer the antibacterial to the end of the first course of treatment or the end of a subsequent course of treatment, if required. The primary end-point was the cost per successfully treated patient. The cost per life saved was also analysed. Various follow-up times were taken into account. Perspective: German National Health Insurance funds. Study population: 1744 patients with intra-abdominal infection. Interventions: Tazobactam/piperacillin (total daily dosage of 13.5 g/day) and imipenem/cilastatin (total daily dosage of 1.5 to 4 g/day). The mean duration of treatment varied from 5.5 to 8.2 days for tazobactam/piperacillin and 5 to 9.4 days for imipenem/cilastatin. Main outcome measure and results: Compared with imipenem/cilastatin, treatment with tazobactam/piperacillin was more effective and the overall treatment costs were lower. In the base-case analysis, the cost-efficacy ratio (cost per successfully treated patient) was 7881 German deutschmarks (DM) for tazobactam/piperacillin and DM11 390 for imipenem/cilastatin. The incremental cost-efficacy ratio (per life saved) varied between -DM72 567 and -DM350 738 for tazobactam/piperacillin. Sensitivity analyses revealed that the results were robust against various assumptions on cost parameters, clinical outcomes and length of treatment. All costs reflect 1998 values; $US1 = DM1.85. Conclusions: This study suggests that compared with imipenem/cilastatin, tazobactam/piperacillin is more cost efficacious in the treatment of intra-abdominal infections and that it offers a cost advantage through fewer relapses and lower daily therapeutic costs.