Take sildenafil as needed before sexual activity. Baseline characteristics of included neonatesa. Shunt direction and severity of pulmonary hypertension; T, treprostinil; S, sildenafil. On the basis of distribution channel, the sildenafil market is segmented into hospital pharmacy, retail pharmacy, online pharmacy and others. Growing geriatric population and rising healthcare expenditure act as an opportunity for market growth.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. Sildenafil (Revatio brand) reduces high blood pressure associated with pulmonary arterial hypertension (PAH). 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.  · Generic Viagra (sildenafil 25mg, 50mg, mg tab) is covered on tier 1 (maximum 4 tabs/month or 49 tablets/year) if you are enrolled in one of these plans: You can request an expedited (fast) exception if you or your doctor believe that your health could be seriously harmed by waiting up to 72 hours for a decision. If your request to.