It has been more than 20 years since Pfizer‘s blockbuster drug Viagra was approved by the Food and Drug Administration to introduce to the U.S. market and even longer since the original patent was granted, yet there are still no generic equivalents available for it.

The original U.S. patent was set to expire in 2012, but Pfizer added a “method-of-use” patent that extended its exclusivity on the drug through this year. (The Canadian government was not having it.)

This is one of many ways pharmaceutical companies game the system to keep generic competition off the market and keep their prices high. Another is with “citizen petitions,” which are, in theory, a way for citizens to raise concerns about pending drug approvals. In reality, 92 percent of citizen petitions are filed by corporations.

These aren’t mere unintended consequences. Rather, they are deliberate measures by the pharmaceutical industry and their extensive campaign finance and lobbying arms to control how the system works. These lobbying efforts are not partisan in nature — they take aim at whichever legislators are expected to assume power after the next election.

Yes, research and development for prescription drugs is very costly, and FDA approvals take years, but Pfizer alone brought in $53 billion in profits in 2018…so I think they are more than recouping their R&D costs.