A report from a team at the University of Wisconsin-Madison notes that Viagra given to rats raised the level of the hormone oxytocin, which is involved in nursing and childbirth and also orgasm and sexual pleasure.  Viagra and related drugs seem to work on the area of the brain that controls the release of this hormone so it is possible that they do more than just help with erectile dysfuntion.

Viagra, Cialis and Levitra inhibit the enzyme phosphodieterase, so aiding the blood flow for erections.  They also affect the posterior pituitary area of the brain and result in a boost of oxytocin; in rats at least but most probably in humans as well.

It has been known for years that oxytocin has a role in childbirth and recently it has been found to be involved with male sexual arousal.

Recent reports have suggested that these drugs are used for fun rather than their prime purpose of helping with erectile dysfunction.  It now seems that there may be a good reason this is happening.  It cannot be stressed too much that these drugs are prescription medicines and not for casual use.  They can have fatal side effects and should only be used with medical supervision.