John’s wort. Efficacy Results from Controlled Clinical Studies The effect on one of the major end points, maintenance of erections after penetration, is shown in Figure 6, for the pooled results of 5 fixed-dose, dose-response studies of greater than one month duration, showing response according to baseline function. If it is not treated right away, priapism can permanently damage your penis sudden vision loss in one or both eyes. The mean times adjusted for baseline to onset of limiting angina were Talk to your doctor about eating grapefruit and drinking grapefruit juice while taking this medicine. Two of the questions from the IIEF served as primary study endpoints; categorical responses were elicited to questions about 1 the ability to achieve erections sufficient for sexual intercourse and 2 the maintenance of erections after penetration.Medically reviewed by Melissa Badowski, PharmD, MPH, FCCP — By Jennifer Mitri Williamson, Pharm.D. — Updated on September 12, Learn about . Why it’s used Sildenafil oral tablet is used to treat ED and PAH. Generic oral tablets are available for both conditions, but the brand-name drugs each treat only one of . Strengths: 25 mg, 50 mg, mg; Brand: Viagra. Form: oral tablet; Strengths: 25 mg, 50 mg, mg; Adult dosage (ages 18–64 years) Typical dosage: 50 mg, taken as needed about 1 hour before.