I wouldn't doubt if he was smoking meth. It causes obsessions with sex, heightens and escalates sex drive.
http://www.sexualrecovery.com/articles/crystal-meth-sex-addiction.php
That makes total sense to me. His obsession is extreme and meth sure is a culprit in that.
We have a huge issue with bath salts or synthetics or whatever you want to call them. But so far, no one has said anything about sex addiction.