Men who experience erectile dysfunction (ED) are unable to achieve an erection sufficient for satisfactory sexual intercourse. One of the most common treatment is with prostaglandin E1 (PGE1), a naturally occurring PGE used to treat this dysfunction. Men either inject PGE1 into their penis or insert a pellet containing the drug into the end of the penis (into the urethra). The review of trials found that men using PGE1 reported more satisfactory sexual experiences. Higher doses gave greater benefits but also increased the adverse effects. The most common adverse effect is some pain, and men may prefer the urethral medication rather than injections.