The substance is the same under both trade names. History Sildenafil compound UK, was synthesized by a group of pharmaceutical chemists led by Simon Campbell [55] working at Pfizer’s Sandwich, Kent , research facility in England. Kidney disease that needs to be treated with dialysis. Often, these are prescribed for chest pain called angina. You are encouraged to report adverse events related to Viatris products by calling U. · Viagra is a brand-name prescription drug approved to treat ED. Viagra contains sildenafil, There are four main types of PDE5 inhibitors: Stendra (avanafil) Levitra, Staxyn ;. The main ingredient in Viagra is sildenafil, meaning that the drugs are essentially the same. However, Viagra is marketed and prescribed strictly for erectile dysfunction, while . Sildenafil tablets for erectile dysfunction come in different strengths ranging from 25mg to mg. The usual dose is 50mg, when you need it. Do not take it more than once a day. The dose can be increased to mg or decreased to 25mg depending on its effect. Take sildenafil up to 4 hours before you want to have sex.