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To most people, “evergreen” refers to a tree that manages to keep its leaves no matter what. But the term has another, highly contentious meaning when discussing prescription drugs — the use of additional patents to extend the monopoly on a medicine and keep cash registers ringing.

Drug makers have long argued their patent modifications reflect substantive enhancements, but the practice has prompted complaints that companies often make minor changes in order to thwart generic competition. And a new study shows the approach may be more pervasive than thought — at least 74 percent of medicines associated with new patents were already on the market.


Moreover, adding new patent protections or an exclusivity was notable among blockbuster drugs. Of the roughly 100 best-selling drugs, almost 80 percent extended patent protection at least once, with almost 50 percent winning added protection more than once, according to the research, which is available online and entitled “May Your Drug Price Be Evergreen,” but has not yet been peer-reviewed in an academic journal.

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