Viagra generics are medicines that have the same qualitative and quantitative composition and the same pharmaceutical form as the original Viagra. Bioequivalence has also been demonstrated by comprehensive bioavailability tests. They are used to treat erectile dysfunction, which is the inability to maintain or achieve an erection. The original Viagra or Sildenafil generics contains the substance Sildenafil Citrate, which is a phosphodiesterase type 5 inhibitor. The patent expired for this substance in many Western European countries in 2013, allowing the use of Sildenafil citrate also within generics. The best known include Kamagra, Slifeldrem or Sildenafil Actavis, Sandos and Mylam.