PHP18: A MODEL FOR COMPARING COSTS ASSOCIATED WITH PRESCRIPTION WASTAGE WITH APPLICATION TO VA PRESCRIPTION DATA

Abstract

OBJECTIVE: The objective of this study was to determine the frequency and cost of prescription switches for 90-day vs. 30-day outpatient prescriptions dispensed by a VA pharmacy and to develop a model to determine the prescription fill policy with the lowest total costs. METHODS: VA outpatient prescription records for one year for simvastatin and lovastatin (30 or 90-days) were analyzed to determine the frequency, quantity and cost of medication wasted due to medication switches. The quantity wasted was defined as the difference between the quantity dispensed and the quantity of drug used before changing to a new drug or dosage. Differences in dispensing costs for a given time-period were also included. Sensitivity analyses were conducted for quantity wasted, drug costs, and dispensing costs. RESULTS: A total of 16,990 prescriptions were analyzed. The quantity and costs of medication wasted were higher for 90-day prescriptions than for 30-day prescriptions. However, average costs to the VA pharmacy were $2.45 higher per prescription for the 30-day supply because of additional dispensing costs for the 30-day fill. The model and sensitivity analyses show that a 90-day supply policy results in lower total pharmacy costs under several scenarios. Only in the case of high drug costs was the 30-day policy favorable to the 90-day policy in terms of total costs. CONCLUSION: Prescriptions given in a 90-day supply resulted in lower total costs. The projected cost savings of having a 90-day versus a 30-day policy would hold true for prescriptions with similar drug costs and similar rates of wastage that result from changes that physicians make to patients' prescriptions. In addition, the model provides a flexible framework for pharmacy administrators to assess refill policies in terms of excess or unnecessary cost for different classes of drugs, given patient and/or physician behavior.