The discussion on when pharma patents expire is often long and tortuous.
The the ED world of Viagra and Cialis we discuss the 2017 patent cliff here.
True, Cialis patent(s) expire in 2017, so it is reasonable to expect the influx of generics soon... Here's a list of patents related to Cialis. Note that there are a lot of patents listed that go all the way to 2020.
Here is a great discussion about the expiration of Phara patents related to Viagra. One of the main patents in viagra falls into the 1995 rule where the expiration date is computed based on the longer of the old method (17 years from issue) and the new method (20 years from first filing date). The 20 years method would be long gone. It probably took Pfizer some very fancy footwork to delay issue of the Viagra patent for almost 10 years from first filing, so the 17 years method computes longest and works best for Viagra. Plus, they got a term extension, so the patent doesn't expire until April of 2020.
But generic Viagra. A settlement with the giant of generics, Teva, allows Teva to sell a generic version of Viagra starting in December of 2017. But Teva must pay royalties to Pfizer. Pfizer recently raised prices, presumably to game this whole competition thing ensuing in 2017.
Levitra faces expiration of patents in 2018.
Great discussion on all these ED drugs is here at AccessRX.
Of course you could use another drug that is "a rose by another name": Revatio. Consumer Reports on Revatiois not in the business of making medical advised, but they suggest the the Revatio blood pressure drug might possibly work in the same way as Viagra since is contains the same active ingredient (sildenafil).
There is also a move to try to make the ED drugs an over-the-counter thing. Hmmm.