While we all learn by rote the principles of safety in an establishment that serves alcohol, not much is said in this environment about what exactly alcohol does. In dealing with customers, it helps to understand exactly what effect alcohol has on the system, which not even many drinkers of alcoholic beverages are aware of.

Alcohol is a potent central nervous system depressant, with a range of side effects. The circumstances of consumption plus the amount consumed play a significant part in determining the extent of intoxication.

Among some of the ways alcoholic effects vary by circumstance, there are: Consuming alcohol immediately after a large meal is less likely to produce visible signs of intoxication than consumption on an empty stomach. Hydration plays a role in the level of intoxication, especially in determining the extent of hangovers. The mood of a person before they started consuming alcohol changes the effect that alcohol will have. Intoxication is more keenly felt when the patron is sleepy, nervous, already intoxicated, under the effects of other drugs, or in certain phases associated with personality disorders.

Alcohol has a biphasic effect on the body, which means that its effects change over time. Initially, alcohol generally produces feelings of relaxation and cheerfulness, but further consumption can lead to blurred vision and coordination problems. Thus a patron who has had five drinks in a row is feeling the combination of these overlapping effects.

Cell membranes are highly permeable to alcohol, so once alcohol is in the bloodstream it can diffuse into almost every biological tissue of the body. After excessive drinking, unconsciousness can occur. Extreme levels of consumption can lead to alcohol poisoning and death. Studies have shown that a concentration in the blood stream of 0.55% will kill half of those affected. Death can also be caused by asphyxiation when vomiting, if it blocks the trachea and the individual is too inebriated to respond.

Intoxication frequently leads to a lowering of one's inhibitions, and intoxicated people will do things they would not do while sober. Sometimes they will even be ignoring social, moral, and legal considerations. However, the personality of the individual does play a role as well. People with a naturally high temper will be more likely to become aggravated, for instance.

The body weight of the individual plays the greatest role in the variety of effects. Eight to ten drinks per hour to a person weighing 120 pounds is considered a fatal dosage, while only being severely inebriating to a person weighing 300 pounds.

Here is a general list of the different concentrations of alcohol in the human body over time and the different effects they have on the subject, listing by Blood Alcohol concentration:

Stage 1: Euphoria (BAC = 0.03 to 0.12 %) The subject may experience an overall improvement in mood and possible euphoria. They may become more self-confident, uninhibited, or daring. Their attention span shortens, similar to the effects of marijuana. They may have a flushed red complexion. Their judgment is impaired, so they may express the first thought that comes to mind, rather than an appropriate comment for the given situation. They have trouble with fine motor skills, such as writing or signing their name.

Stage 2: Lethargy (BAC = 0.09 to 0.25 %) Subject may become sleepy or listless. They have trouble understanding or remembering things, even recent events - again like the short-term memory loss with marijuana. Their reaction time slows down. Their body movements are uncoordinated; they begin to lose their balance easily, evident in stumbling wile walking and tipping things over when reaching for them. Their vision becomes blurry, and they may have trouble sensing things.

Stage 3: Confusion (BAC = 0.18 to 0.30 %) Profound confusion occurs. They may be uncertain where they are or what they are doing. Dizziness and staggering occur. A heightened emotional state happens, in which they may become aggressive, withdrawn, or overly affectionate. Vision, speech, and awareness are severely impaired, with extremely poor coordination and pain response. this is the stage at which nausea and vomiting often occur.

Stage 4: Stupor (BAC = 0.25 to 0.40 %) Movements are severely impaired. The subject will exhibit lapses into and out of consciousness. They may have 'blackouts', where they do not remember large chunks of time. They may 'pass out' into a heavy slumber. Subjects can slip into a coma at this stage, and there is also a risk of death if they aspirate vomit while semi-conscious.

Stage 5: Coma (BAC = 0.35 to 0.50 %) Unconsciousness sets in. Reflexes are depressed, for instance the pupils do not respond appropriately to changes in light. The subject's breathing is slower and more shallow, their heart rate drops, and death usually occurs at levels in this range.

Stage 6: Death (BAC more than 0.50 %) Alcohol causes central nervous system to fail, resulting in death.

Keep in mind that this isn't a doctor's opinion, but rather a general guide. Very few people manage to achieve BACs higher than 0.40%, since under normal drinking circumstances this is when the body either rejects further consumption by vomiting, or causes the subject to 'pass out' asleep.

The circumstances of the individual prior to consumption are not to be taken lightly. People who suffer from psychological problems may ignore the danger of mixing alcohol with their prescription medications. Particularly sufferers of manic-depression are a category of people who may feel over-confident at certain phases and will proceed to drink quite heavily, endangering their health. People taking anti-depressants also have to be careful, as many anti-depressant medications have severe health risks when mixed with alcohol.

One thing you might not also think of is whether the subject has recently donated blood. Since donating a pint of blood at a blood bank lowers the person's total blood, alcoholic beverages will produce a significantly higher BAC than under normal circumstances. Although donors are warned not to drink alcohol immediately after donating blood, some college students do exactly this, engaging in binge drinking after giving blood, because they can feel a more intense buzz for the same price.

For further information in this field, seek the advice of a professional physician.