A Model for Comparing Unnecessary Costs Associated with Various Prescription Fill-Quantity Policies: Illustration Using VA Data

OBJECTIVE: To describe a model for analyzing the unnecessary costs associated with outpatient prescription fill quantities and to apply the model to prescription data from the Veterans Administration’s Chicago Health Care System (VACHCS) to examine costs under various scenarios. DESIGN: The model developed here included the cost of drugs, quantity of drug wasted, and the cost to fill the prescription, and is used to determine and compare the total unnecessary costs (TUC) of different prescription fill quantities. The model was applied to the VACHCS outpatient prescription records for two formulary hydroxymethyl glutaryl coenzyme A (HMGCoA) reductase-inhibitor drugs to determine TUC for 30- and 90-day fills. Sensitivity analysis was used to analyze changes in the TUC over a range of possible values for each variable in the model. RESULTS: A total of 16,990 prescriptions met the study inclusion criteria, of which 21.4% were for a 30-day supply and 78.6% for a 90-day supply. For 30-day and 90-day prescriptions, the average prescription cost per day was $0.56 and $0.54, respectively; quantity wasted was 1.06 days and 5.33 days; and TUC per prescription were $5.62 and $3.17. Sensitivity analysis demonstrated that the 90day policy maintained lower TUC for most scenarios with the exception of very high drug costs. CONCLUSION: Prescription benefit managers will find this model informative for determining policies for prescription fill quantities.