Sildenafil (Viagra), which is approved to treat erectile dysfunction, could now be taken daily to prevent it, a high profile professor of urology has advised.

Professor Irwin Goldstein of Boston University, Massachusetts, said at a recent continuing medical education event (sponsored chiefly by the drug's manufacturer, Pfizer) that he was a “strong believer” in taking sildenafil on a daily basis to “prevent impotence.”

Before a large audience of primary care doctors and others attending a sexual function update at New York University in December, Professor Goldstein said he had “hundreds of men” using Viagra for prevention: “If you would like to be sexually active in five years' time, take a quarter …