Manufacturer revenue on inhalers after expiration of primary patents, 2000-2021

Inhalers remain the cornerstone therapy for patients with asthma and chronic obstructive pulmonary disease (COPD). Over the past several decades, brand-name manufacturers have continued to sell most inhalers at high prices without the threat of direct generic competition. They have arranged for long periods of market exclusivity by obtaining patents not just on the active ingredients (primary patents) but also on peripheral aspects of these products, such as the propellants and delivery devices (secondary patents), and by shifting active ingredients to different devices (device hops), thereby adding new secondary patents.