The Utilization of Medicines beyond Patent Expiration

摘要

BACKGROUND: The utilization of a medicine, both before and after patent expiration, isnone of the key determinants of its long-run value to society, as consumer and producer surplusnaccumulate as utilization occurs. However, while utilization during the years of patent protectionnis followed fairly closely, usage after that is generally not, as multiple manufacturers are usuallyninvolved in the production and sale of generic alternatives. Since utilization beyond patent expirationnis poorly understood, we selected a random sample of 60 drugs and assessed their long-term,npost-patent use during the period of generic competition.nMETHODS: At five-year intervals beginning with the year generic competition began (YGCB),nwe estimated the U.S. utilization of each drug (including all generic and branded formulations)nbased on the number of prescriptions dispensed as projected by the National Prescription AuditTMn(1964 to 2006) conducted by IMSTM. These estimates were then compared to each medicine’snbaseline utilization, defined as the drug’s usage during the last full year of patent protection – onenyear prior to the year generic competition began (YGCB-1). The absolute utilization levels werenconverted into relative utilization levels, whereby a measure of 1.0 indicates that utilization in thatnyear was equal to utilization in the baseline year.nRESULTS: Many drugs continued to be prescribed long after patent protection ended. Even afternexcluding one medicine that had unusually high utilization 15 to 30 years after generic competitionnbegan, relative utilization averaged between 0.64 and 0.99 for the 5-year intervals startingnwith YGCB+5 and ending with YGCB+30. This was true even though several of the medicinesnwere available over-the-counter (OTC) during some of those years and we did not have data reflectingnOTC utilization. After excluding those OTC years (to focus on medicines that had morencomplete data), relative utilization averaged between 0.88 and 1.15. CONCLUSION: Many medicines continue to be used far beyond their period of patent protection,nsomewhat countering the view that newer drugs quickly replace older ones. This extended,npost-patent utilization can yield additional surplus for society that is over and above the surplusngenerated during the period of patent protection.