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. Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. Box , Mission, KS If your pharmacy does not participate, you may be able to submit a request for a rebate in connection with this Savings Offer. Be sure to let your doctor and pharmacist know that you are taking these medications before you start taking sildenafil. Similar values for pharmacokinetic parameters were seen in normal volunteers and in the patient population, using a population pharmacokinetic approach. Sexual function data were also recorded by patients in a daily diary.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. Sildenafil is available through Roman by prescription in , , mg pills and ranging in price from $4–$10 per dose. Brand-name Viagra is also available through Roman in , , mg. Sildenafil citrate is a white to off-white crystalline powder with a solubility of mg/mL in water and a molecular weight of VIAGRA is formulated as blue, film-coated rounded-diamond-shaped tablets equivalent to 25 mg, 50 mg and mg of sildenafil for oral administration.