The effects of differences in state drug product selection laws on pharmacists' substitution behavior

The objective of this project was to examine and quantify the effects of specific requirements of state drug product selection (DPS) laws on pharmacists' generic drug substitution practices. The specific requirements on which state laws differ included, for example, whether the law mandated or simply allowed DPS, whether some type of formulary was required, and whether pharmacists were required to pass on cost savings to consumers. Data on state DPS laws were found in the National Association of Boards of Pharmacy's annual Surveys of Pharmacy Law and by contacting state boards of pharmacy. Estimates of state substitution rates were provided by IMS, America. Multiple regression analysis was employed to estimate the effects of legal requirements on substitution rates. Results indicated that substitution was more prevalent in states that did not require additional record keeping and in those that did require patient consent prior to substitution. The relationship between formulary restrictions, requirements regarding the passing on of savings, and liability limiting laws and substitution rates differed significantly between those states that required a two-line prescription form and those allowing use of one-line forms. Three nonlegal variables--time the DPS law had been in effect, percent of generic prescribing in the state, and mean pharmacist age--were also associated with substitution rates.