When totally off his face at a friend's 18th he ran around saying this quite comical phrase hoping to arouse a few people (or so I have heard) or just for the sheer comic value.
In essence it is a mixture of ''pissed'' and ''drunk''. However, when inhibited by alcohol, a persons vocabularical skills somewhat take a severe turn for the worse. This results in both ''pissed'' and ''drunk'' being brought together to form ''pissdrunx''. The last X was added due to this person sluring their words.
Im so pissdrunx its not funny
Me: Want another Magners
Jamie: No, im too pissdrunx to take one.