@perennialloner,
												The difference is that Drunken should be used in front of a noun whereas Drunk should be used after a verb. 
For example, He was a drunk." (used as a noun), or "He was too drunk to drive." (used as an adjective).
 "He was a drunken mess." You can't call someone "a drunken", so that's where they differ grammatically, I think.