Researchers at Johns Hopkins and other institutions are currently testing a suppository made from prostaglandin E1, which is presently available as an injectable solution. The suppository can be inserted into the urethra using a slender plastic tube. Once inside, the prostaglandin diffuses across the delicate urethral membrane toward the blood vessels located inside the penis. As a result, the blood vessels widen, more blood enters the area, and the penis becomes erect. Suppositories can probably be used more often than injections, with less risk of penile scarring, shape changes, and prolonged erections - although further study is needed to confirm this hypothesis.
Researchers have also examined the possibility of using topical creams and sprays containing prostaglandin and other drugs (such as minoxidil, the baldness remedy known as Rogaine, and nitroglycerin) but according to Richard Allen, PhD, assistant professor of neurology at Johns Hopkins, while these approaches may help some patients, they'll probably be less effective than the suppository, because the tough skin on the penis hinders absorption.