Prostaglandin E-1 (PGE-1) is a naturally occurring hormone that helps maintain an erection during sexual activity. Prostaglandin E-2 (PGE-2), on the other hand, is a synthetic version of PGE-1 and can be used as a more potent version of PGE-1.
The main difference between these two compounds is their effectiveness at dilating blood vessels in your penis, resulting in an erection.