Tadora 20 mg contains the active ingredient Tadalafil, which is used to treat erectile dysfunction. Tadalafil is also the active ingredient in the brand-name medication Cialis. The patent for Cialis (containing Tadalafil) was initially held by Eli Lilly and Company. The original patent for Cialis was set to expire in 2016. However, due to various legal challenges and settlements, the patent expiration was extended to September 27, 2018, in the United States. This allowed other pharmaceutical companies to start producing generic versions of Tadalafil after the patent expiration. As a result, generic versions of Tadalafil, including medications like Tadora 20 mg, became available in the market shortly after the patent expiration in September 2018. It's important to note that patent expiration dates can vary by country and region, so the availability of generic versions might have occurred at different times in different parts of the world.