Viagra 100mg working time: Viagra is most effective when

Viagra is most effective when taken in this time frame since it takes a little while for the medication to circulate and stimulate an erection. However, Viagra may be taken up to 4 hours before sexual activity and still be effective. Viagra lasts for up to 4 hours. The average time of onset is 60 minutes. The effects vary for each individual. Learn more about how long Viagra lasts here. How Long Does It Take for Sildenafil to Work? Typically, it takes half an hour to one hour for Sildenafil to start working, so you should allow for that suggested timeframe before engaging in sexual intercourse. It may be reassuring however, that after you take it, it can last for up to four hours in your system. Viagra (sildenafil) is used to treat erectile dysfunction or impotence in men. Includes Viagra side effects, interactions and indications.