During 3 to 6 months of double-blind treatment or longer-term 1 year , open-label studies, few patients withdrew from active treatment for any reason, including lack of effectiveness. If you are taking sildenafil for PAH, take the missed dose as soon as you remember it. Data shared with Viatris will be aggregated and de-identified; it will be combined with data related to other Savings Offer redemptions and will not identify you Viatris reserves the right to rescind, revoke, or amend this Savings Offer without notice No membership fees. Trimazosin Other Interactions Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Do not use more of it and do not use it more often than your doctor ordered. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine. Sildenafil is in a class of medications called phosphodiesterase PDE inhibitors.Examples of Viagra’s more commonly reported side effects include: headache. flushing (temporary warmth, redness, or deepening of skin color) stuffy nose. indigestion (upset stomach) mild vision. Rarely reported side effects include: an erection that will not go away (priapism). If you have an erection that lasts more than 4 hours, get medical help right away. If it is not treated right away, priapism can permanently damage your penis. sudden vision loss in one or both eyes. Generic Viagra (sildenafil) is an alternative to the branded Viagra drug that can be used for treating erectile dysfunction (ED). It’s now sold by many manufacturers, including online.