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. Maximum observed plasma concentrations are reached within 30 to minutes median 60 minutes of oral dosing in the fasted state. Other uses for this medicine This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information. The primary measure in the principal studies was a sexual function questionnaire the International Index of Erectile Function – IIEF administered during a 4-week treatment-free run-in period, at baseline, at follow-up visits, and at the end of double-blind, placebo-controlled, at-home treatment. Therefore, inhibitors of these isoenzymes may reduce sildenafil clearance and inducers of these isoenzymes may increase sildenafil clearance. Tell your doctor if sildenafil is not working well or if you are experiencing side effects. 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.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. 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. Sildenafil (Viagra, Revatio) is a moderately priced drug used to treat erection problems in is also used to treat pulmonary arterial hypertension, a serious heart and lung drug is more popular than comparable drugs. It is available in generic and brand versions. Generic sildenafil is covered by most Medicare and insurance plans, but .