When I was doing some research on Distilling for a personal project I came across this information:
Chronic users develop a tolerance to ethanol. Ethanol depresses the central nervous system irregularly in descending order from cortex to medulla, depending on the amount ingested. The range between a dose that produces anesthesia and one that impairs vital functions is small. Thus, an amount that produces stupor is dangerously close to a fatal dose. Effects are potentiated by concomitant ingestion of barbiturates and other depressant drugs.
Intoxication levels (broadly) are found in this manner:
Mild (Blood alc content 0.05%-0.15% - one fourth of the people at this level are clinically intoxicated) results in decreased inhibition, slight visual imparement, muscular incoordination, and slowed reaction time.
Moderate: (BAC: 0.15%-0.3% - 50 to 95% of the people at this level are clinically intoxicated)- results in definite visual imparement, sensory loss, muscular incoordination, slurring of speech.
Severe (BAC 0.3%-0.5% -fatalities begin to occur in this range)-marked muscular incoordination, blurred vision, approaching stupor.
Coma (BAC above 0.5% - death is common in this range)- Unconsciousness, slowed respiration, complete loss of sensations.