The immediate physical effects of drinking alcohol range from mild mood changes to complete loss of coordination, vision, balance, and speech. These can be signals of acute alcohol intoxication, or drunkenness. These effects usually wear off in a matter of hours after a person stops drinking. Many law-enforcement agencies regard a .08 percentage of alcohol in the bloodstream as evidence of intoxication. Larger amounts of blood alcohol can impair brain function and eventually cause unconsciousness. An extreme overdose, alcohol poisoning, can be fatal.