Variations in time of market exclusivity among top-selling prescription drugs in the United States.

Variations in Time ofMarket Exclusivity Among Top-Selling Prescription Drugs in theUnited States In the United States, effective market exclusivity for a prescription drug is the time between US Food and Drug Administration (FDA) approval and the availability of the first generic version. Market exclusivity incorporates the minimum regulatory exclusivity periods granted to all FDA-approved drugs (eg, 5 years for newsmall-molecule drugs as set by theHatch-WaxmanAct of 1984), the remaining time on the original patent covering the active ingredient in the drug, the existence of so-called secondary patents covering peripheral aspects of drugs such as metabolitesor alternative formulations,1 andother factors that affect generic entry, such as generic manufacturers’ prospects of profit-making in themarket and legal settlements between manufacturers of brand-name and generic drugs regarding disputed patents. Recent research has shown that prescription brand-name drugs that eventually face generic competition have, on average, an effective market exclusivity period of 12.4 years.2 We assessed how the market exclusivity period varied among drugs for different therapeutic areas and for other characteristics of top-selling prescription medications. Methods | This study was not submitted for institutional review board approval because it is based on publicly available data and involvednohealth records.Weobtained annual published listsbetween2000and2011of the top200drugsbysales in the United States. We classified each agent into a primary therapeuticarea.UsingMedicaidprescriptiondatacompiledby the Centers for Medicare &Medicaid Services, we determined if a brand-name drug experienced generic competition from 2000 to 2012.3 We defined initiation of generic competition as the first quarter inwhich generic prescriptionswere filled. For the subset of drugs that lost market exclusivity, we used the Drugs@FDAdatabase4 to identify the approval date, chemical type (newmolecular entity or new formulation), andwhether thedrugreceivedapriority review.Wedeterminedwhether the FDAgrantedeachdrugaspecialdevelopmentaldesignation(orphan drug, accelerated approval, or fast-track status).5 For all drugs that were new molecular entities and became generically available, we used a framework developed by the FDA to categorizetheir innovativenessandthesizeof thecompanythat sponsored their FDA applications based on sales revenue.6We performedWilcoxon rank sum and Kruskal-Wallis tests to examine differences among our comparison groups of drugs.