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. They include dutasteride Avodart, Jalyn and finasteride Propecia, Proscar. Some people buy sildenafil online without a prescription. If you are taking sildenafil to treat PAH, you will probably take sildenafil three times a day with or without food. If you see air bubbles in the syringe, repeat the steps. Before taking sildenafil, tell your doctor and pharmacist if you are allergic to sildenafil, any other medications, or any of the ingredients in sildenafil tablet or suspension. If you have erection problems sildenafil works by temporarily increasing blood flow to your penis when you get sexually excited.Sildenafil (Viagra) is often the first drug your doctor offers. It’s been on the market longest and its side effects and the medications and foods it interacts with are well known. But . Erectile dysfunction is when a man has difficulty getting an erection or keeping it long enough for sex. It’s also known as ED or impotence. It happens when not enough blood flows to the penis, preventing an erection. The frequency increases with age, affecting about 50% of men over age 40*; however younger men may also experience ED. Sildenafil (Viagra). This medicine works best when you take it on an empty stomach an hour before sex. The body takes longer to absorb it after a high-fat meal or alcohol. Its effects .