You need a prescription from a doctor to obtain sildenafil. Sildenafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow easily. Flibanserin is not approved in Australia. What should I do if I forget a dose? Taking generic ED medications is an effective way to save money without sacrificing quality.Sildenafil (Viagra) is a medicine used to treat erectile dysfunction (ED, also called impotence). Sildenafil works by helping to relax the blood vessels in the penis, allowing more blood to flow in and cause an erection. You should take sildenafil about an hour before planned sexual activity, so it has time to work. When samples of milligram Viagra tablets purchased online were tested, only 10% were even close to the advertised strength. When you buy from an unknown company, . 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.