Cost-minimization analysis of Imipenem/Cilastatin versus Meropenem in moderate to severe infections at a tertiary care hospital in Saudi Arabia.
Introduction: The aim of this study was to compare the costs of management of moderate to severe infections in patients treated with imipenem/ cilastatin (IC) and meropenem (MEM). Pharmacoeconomic studies in Saudi Arabia are scarce. Available hospital data illustrate that carbapenem antibiotics are among the most expensive medicines being procured. The current hospital formulary at the King Abdulaziz National Guard Hospital, Al-Ahsa, Saudi Arabia, contains 2 carbapenems: IC and MEM. These antibiotics share a similar spectrum of activity, with the unit cost of IC (500mg/ 500mg) being less than that for MEM (1 gram). There are conflicting reviews with regard to the relative cost-effectiveness of these 2 agents. An unpublished pharmacoeconomic review at our institute has shown that an interchange programme substituting MEM with IC would lead to a cost saving of SAR2 306 257 per year. Methods: A retrospective, single-centre cohort study of 88 patients, applying cost-minimization analysis, of IC versus MEM in moderate to severe infections was conducted at the King Abdulaziz National Guard Hospital, Al-Ahsa. In accordance with cost-minimization analysis methods, the assumption of equivalent efficacy was demonstrated by literature retrieved and cited. Direct costs related to the management of the infections were included in the study. Adult patients (≥18 years old) diagnosed with moderate to severe infection, including skin and skin structure infections (SSIs), sepsis, intra-abdominal infections (IAIs), respiratory tract infections, urinary tract infections (UTIs) and hospital-acquired infections (HAIs), who were prescribed IC 500mg every six hours intravenously (2 gram per day) or MEM 1 gram every eight hours (3 gram per day), were included in the study. Results: Overall there was no difference in the mean total daily costs between IC (SAR 4 784.46, 95% CI 4 140.68, 5 428.24) and MEM (4 390.14, 95% CI 3 785.82, 4 994.45;, p = 0.37). The study showed no significant difference in terms of mean daily critical care hospital stay costs. Mean general ward costs were significantly lower in the IC group. Significantly lower medicine acquisition vial cost of IC was observed when compared to MEM, however there was a significantly higher cost attached to administration sets used in the IC group than the MEM group. Consultation, nursing and physician costs were not significantly different between the groups. No differences were observed in costs associated with adverse drug events (ADEs). Conclusion: This study has shown that while acquisition costs of IC at a dose of 500mg q6h may be lower than for MEM 1 gram q8h, mean total costs per day were not significantly different between IC and MEM, indicating that medicine costs are only a small element of the overall costs of managing moderate to severe infections. Enforcing the Pharmacy and Therapeutic Committee (PTC) recommendations will assist in selecting the most appropriate carbapenem, while at the same time minimize drug costs. Further pharmacoeconomic research within the Kingdom of Saudi Arabia is essential in selecting cost-effective medicines.