Teva sued to have the latter patent invalidated, but Pfizer prevailed in an August federal district court case. Viagra is also informally known as “vitamin V”, “the blue pill”, or “blue diamond”, as well as various other nicknames. Rarely reported side effects include: an erection that will not go away priapism. The patent on Revatio indicated for pulmonary arterial hypertension rather than erectile dysfunction expired in late Especially tell your healthcare provider if you take any of the following: medicines called nitrates medicines called guanylate cyclase stimulators such as Adempas riociguat medicines called alpha-blockers, such as Hytrin terazosin HCl , Flomax tamsulosin HCl , Cardura doxazosin mesylate , Minipress prazosin HCl , Uroxatral alfuzosin HCl , Jalyn dutasteride and tamsulosin HCl , or Rapaflo silodosin. Food and Drug Administration has approved fifteen drug manufacturers to market generic sildenafil in the United States. Sildenafil is also used in both men and women to treat the symptoms of pulmonary arterial hypertension.Brand names: Viagra, Revatio. Sildenafil comes in three forms: an oral tablet, an oral suspension (liquid), and an injection that’s only given by a doctor. .  · Teva sildenafil is a generic version of Viagra that’s sold and branded by a different company. This means that it’s typically sold for much lower prices since no marketing dollars are needed. Sildenafil (Viagra brand) only works following sexual stimulation. It works within 30 to 60 minutes, but may be taken up to four hours before sexual activity. Revatio is available as a generic under the name of sildenafil (20mg tablet). There is also a generic version of Viagra available, under the name sildenafil, in 25mg, 50mg, and .