Alprostadil is the pharmaceutical name for prostaglandin E1. It is used as a drug in the treatment of erectile dysfunction. I know that there is one kind that you stick in your dickhole just before sex. Sounds like fun. Another type is Caverject, which you have to inject into your penis, also just before sex. Neither sounds like a good time to me, but to each his own.
I think that this route of ED treatment has been commonly replaced with things like viagra, cialis, etc. as they are more effective and easier to use.