The manufacturer of Viagra claims that the drug can shorten the time it takes a man to recover after sex and be ready for another round. This is called the “refractory period.” Normally it lasts 20 minutes or longer. One study, published in the journal Human Reproduction in January 2000, found that Viagra shortened the refractory period by about 10 minutes in healthy men. However, Viagra (and as for any other ED drugs) cannot increase your sexual appetite or make you ejaculate if you have problems reaching orgasm

They aren’t “enhancement drugs,” they simply increase bloodflow to the penis (and other areas).
They may not have necessarily negative effects on younger patients, but they will not likely have any positive effects, either.

This would fall under the description of recreational use of these drugs: enhancing your performance when none is required.