Erectile dysfunction drugs have come as a major boon for many men with sexual performance problems. In some cases, they offer a quick fix to a problem that may have taken some men out of the game. However, these medications are not without a certain degree of risk.

Most people are now familiar with one of the most serious side effects of these medications thanks to TV advertisements, which warn men to call their doctor if they experience an erection lasting more than four hours. If this occurs, it can cause serious damage to tissue in the area and hamper male sexual function.

Dr. Kenneth Peters, chairman of the urology department at Beaumont Hospital in Royal Oak, Michigan, told the Detroit Free Press that the effect of a four-hour erection is similar to what would be experienced in any part of the body that is deprived of oxygenated blood.

“So if you have an erection that lasts too long, there’s no new oxygen going to the penis, so what can happen is that you can actually develop tissue injury because of lack of blood flow, just as you would if you cut off the flow of fresh blood to the arm or the heart,” he told the news source.