Skip to main content
DrugPrice

Evergreening

Strategies drug manufacturers use to extend patent protection beyond the original expiration, including new formulations, delivery methods, or minor modifications.

How It Works

Evergreening (also called "product hopping" or patent thicketing) uses secondary patents and minor modifications to extend exclusivity beyond primary patents. Tactics include: (1) patent thickets, layering dozens of patents on formulations, dosages, manufacturing processes, and methods of use, AbbVie filed 132 patents on Humira spanning its U.S. life; (2) product hopping, switching patients from an original formulation to a reformulated version (Namenda IR to Namenda XR) before generic entry, making generic substitution clinically impractical; (3) polymorph and crystal-form patents, claiming specific crystalline forms of the active ingredient; (4) method-of-use patents for secondary indications filed years after original approval; (5) delivery-system patents, switching from tablet to autoinjector or long-acting formulation; (6) combination-drug patents combining existing drugs into single pills. The FTC has challenged several evergreening practices as anti-competitive, including the Namenda XR product hop (Second Circuit affirmed FTC win in 2015) and multiple Orange Book listing challenges in 2023. The "I-MAK" report published in 2022 found the top 12 Medicare drugs averaged 125 patent filings per drug with 38 years of potential exclusivity from filing. IRA negotiation eligibility uses the original FDA approval date, not subsequent secondary patent filings, which limits the utility of evergreening for extending negotiation-free status. Europe and Canada generally apply stricter patentability standards to follow-on patents, resulting in earlier generic entry for many drugs whose U.S. exclusivity is extended by evergreening.

Related Terms

  • Patent Expiration, The date when a drug's patent protection ends, allowing generic or biosimilar manufacturers to produce competing versions.
  • Patent Cliff, A sharp drop in a drug's revenue when its patent expires and generic competitors enter the market, often cutting prices by 80% or more.
  • Exclusivity Period, A period of market protection granted by the FDA (separate from patents) during which generic competitors cannot be approved, even if no patent exists.
  • Orange Book Listing, The FDA's publication of approved drug products with therapeutic equivalence ratings and associated patent and exclusivity information, used to determine generic substitution.

Explore Drug Data

Most Expensive DrugsGeneric Drug WatchSearch All Drugs

About This Definition

This definition is part of the DrugPrice Drug Pricing Glossary, 49 terms explaining how prescription drug pricing works in the United States. All definitions are written in plain language for patients, caregivers, journalists, and healthcare professionals.

this entity is one of the U.S. Medicare prescription-drug pricing concepts that recurs across this site. The definition above is the technical answer; the paragraphs below add the practical context for how the concept connects to the CMS Medicare Part D Drug Spending data data behind every per-entity page on the site.

In the CMS Medicare Part D Drug Spending data data, this concept shapes one or more of the fields that drive the per-entity grades and rankings on this site. The methodology page describes which fields feed into which output; this glossary entry documents the underlying term.

Source: CMS Medicare Part D Spending, 2026.