Evaluation and financial impact of imipenem/cilastatin dosing in elderly patients based on renal function and body weight

Objective: To evaluate the financial impact of adjusting imipenem/cilastatin (IC) dosages in elderly patients based on estimated creatinine clearance (CI(cr)) and body weight. Design: Retrospective cost- savings analysis. Setting: A 500-bed, university-affiliated, tertiary-care hospital. Main Outcome Measures: All courses of IC administered to patients over age 60 during a four-month period were retrospectively assessed for appropriateness based on both dosing interval and dosage. Manufacturer's guidelines for adjusting the IC dosage based on estimated Cl(cr) and body weight were used to define appropriate dosing. The cost savings that could have been realized by appropriately adjusting IC dosage was calculated for the study period and extrapolated to project an annual cost savings. Results: Only 37 percent of patient days of therapy and 32 percent of therapy courses were judged as appropriate based on both dose amount and interval. The projected annual cost savings that could have been realized by appropriately adjusting IC dosage based on estimated Cl(cr) and body weight was $11,550. Conclusions: Adjustment of IC dosages in elderly patients based on estimated Cl(cr) and body weight can result in significant cost savings.