Cialis: Is one right for you? If you have certain health conditions or are taking certain medications, your doctor may tell you to take sildenafil less often. This increased blood flow can cause an erection. Sildenafil usually should not be taken more than once every 24 hours. Your healthcare provider will discuss which dose is right for you. VIAGRA was evaluated primarily at doses of 25 mg, 50 mg and mg in 21 randomized, double-blind, placebo-controlled trials of up to 6 months in duration, using a variety of study designs fixed dose, titration, parallel, crossover.Rarely reported side effects include: an erection that will not go away (priapism). If you have an erection that lasts more than 4 hours, get medical help right away. If it is not treated right away, priapism can permanently damage your penis. sudden vision loss in one or both eyes. Generic Viagra (sildenafil) is available as a , , , and milligram (mg) pill and in liquid form. It’s meant to be taken as needed — about an hour before sex — but shouldn’t be. Top 10 Best Viagra in Los Angeles, CA – November – Yelp – Rite Aid, Stem Cell & PRP Institute of L.A., Mitsuwa Marketplace, Tan Binh Pharmacy, Marina Gold, MD, Mini Pharmacy Enterprises, CVS Pharmacy, Clifford Segil, DO, Jeffrey Gramer, MD, Ralphs.