The body takes longer to absorb it after a high-fat meal or alcohol. Popular searches. There were highly statistically significant improvements on the two principal IIEF questions frequency of successful penetration during sexual activity and maintenance of erections after penetration on VIAGRA compared to placebo. This is consistent with ritonavir’s marked effects on a broad range of P substrates. The concomitant use of erythromycin or strong CYP3A4 inhibitors e. It lasts 4 to 5 hours, or longer if you have mild to moderate ED. Effects of sildenafil citrate on ejaculation latency, detumescence time, and refractory period: placebo-controlled, double-blind, crossover laboratory setting study.Still, if your doctor says it’s okay for you to use and you end up paying out-of-pocket, you can still get the generic for a lot less than Viagra. According to price . Viagra is absorbed quickly into your body. It can start working within 30 minutes, but it may take a couple hours for some people. However, one study on Viagra found that about 70% of men achieved erections in 30 minutes, and more than 80% of men achieved erections within 45 minutes. For most men, the effects of Viagra will start within . Sildenafil (Generic Viagra, Revatio) is medication used to treat erectile dysfunction (ED) in men who suffer from impotence, or the inability to get or maintain an combination with sexual stimulation, sildenafil works by increasing blood flow to the penis to help a man get an erection and maintain it during sexual intercourse.