The active ingredient of Viagra is sildenafil citrate. Pfizer Inc is the only pharmaceutical company that holds worldwide patents on sildenafil citrate, and so no other manufacturer can make sildenafil citrate and sell it under any brand name as generic Viagra until Pfizer’s patents expire (most of them expire in 2011–2014).

But many bad companies and dealers have been making lots of generic Viagra, most of which comes from India, China, and other third world countries were law enforcement is limp.

In addition to being illegal, a lot of the generic Viagra sold online for low prices was found to contain unknown, unapproved, and/or dangerous ingredients, which may lead to serious side effects or even death in some cases.

But does it work?

Yes, there are still a few “good” manufacturers who make “decent” generic Viagra (sildenafil citrate tablets), which works the same way as brand Viagra.

Many experts expect Cialis to overthrow Pfizer’s little blue pill (Viagra) in the upcoming years, which just makes sense.

Lilly has been more creative with their brand and advertisements for Cialis than Pfizer has been with their Viagra plans.

If Pfizer does not start getting more creative and creating more compelling commercials for their erectile dysfunction drug, Cialis will very soon take over Viagra’s spot as the #1 ED medication.