I would put that under the Remove Poison level, since alcohol is a poison. So it is a 9th level Mercy.
Drunkeness: drunk creatures are sickened which is 3rd level mercy. Alcoholism is addiction and addictions are typed as disease (removing diseases is 6th level mercy but someone unwilling to be cured of alcoholism may make a Fortitude saving throw). More exotic alcohols might be treated as drugs/poisons and affected with neutralize poison as noted by Vod.