The studies that established benefit demonstrated improvements in success rates for sexual intercourse compared with placebo. Mean sildenafil plasma concentrations measured after the administration of a single oral dose of mg to healthy male volunteers is depicted below: Figure 5: Mean Sildenafil Plasma Concentrations in Healthy Male Volunteers. The major circulating metabolite results from N-desmethylation of sildenafil, and is itself further metabolized. The pharmacokinetics of sildenafil are dose-proportional over the recommended dose range. Stop taking VIAGRA and call your healthcare provider right away if you have any sudden vision loss sudden hearing decrease or hearing loss. The possible categorical responses to these questions were 0 no attempted intercourse, 1 never or almost never, 2 a few times, 3 sometimes, 4 most times, and 5 almost always or always. Patients should always ask their doctors for medical advice about adverse events.That’s compared with more than $50 per pill for Viagra. And while generic Revatio is available only in a mg strength—Viagra comes in , , and mg tabs—not to worry: Your doctor can. Extra 15% off $30 sitewide with code SAVE15; Clip your mystery deal! BOGO 50% off select Walgreens health & wellness. What Happened When I Took Viagra Recreationally. 1. Viagra was effective for much longer than four hours. Shutterstock. Viagra comes in three different sizes: 25mg, 50mg, or mg. In the past, I’ve found that 25mg always did the job just fine. However, my journey begins with a bottle of the mg tabs which I’ve chosen to cut into thirds.