You certainly should act to protect yourself or innocent third parties (children and pets) who can't protect themselves. The question is always the best way to do that. Trying to control the alcoholic's drinking is a pretty ineffective way to do that. The best way is to remove yourself or the others who would be endangered from the source of the danger. If he's driving drunk, calling the police can protect innocents who might be hurt. If his drinking is endangering his livelihood then your best course of action is to take steps to protect yourself financially.