As a central nervous system depressant, alcohol can kill just as easily as narcotics (e.g. heroin), barbiturates (downers), or other sedatives.
With high-risk drinking, the concentration of alcohol in the brain becomes high enough to depress the areas of the brain responsible for consciousness and respiration. As a result, the drinker can lapse into a coma, stop breathing, and die.
Alcohol depresses nerves that control involuntary actions such as the gag reflex, which prevents choking. Since alcohol irritates the stomach, people who drink an excessive amount often vomit. Without a properly functioning gag reflex, there is a risk of choking on vomit, which could kill an unconscious person.
A person's blood alcohol concentration (BAC) can continue to rise even while passed out as alcohol in the stomach and intestine continues to enter the bloodstream. Assuming the person will "sleep it off" is dangerous. Also, forcing the person to vomit does not help. The alcohol has already passed into their small intestine and they cannot vomit those contents. Other common myths about sobering up include drinking black coffee, taking a cold bath or shower, or walking it off. It's important to know that none of these things will help a person sober up, and they have the potential to cause more harm than good. The only thing that can help a person sober up is time.
If a person is so intoxicated to the point that they are completely non-responsive, not breathing, or showing any of the other signs of alcohol poisoning, get help immediately. Call 911.