Alcohol's Properties
Alcohol is a general term denoting a family of organic chemicals with common properties. Members of this family include ethanol, methanol, isopropanol, and others. This introduction discusses the physical, chemical, and physiological aspects of the most commonly ingested of these - ethanol.
Alcohol (ethanol) is a clear, volatile liquid that burns (oxidizes) easily. It has a slight, characteristic odor and is very soluble in water. Alcohol is an organic compound composed of carbon, oxygen, and hydrogen; its chemical formula is C2H5OH.
Alcohol is a central nervous system depressant and it is the central nervous system which is the bodily system that is most severely affected by alcohol (see chart below). The degree to which the central nervous system function is impaired is directly proportional to the concentration of alcohol in the blood.
When ingested, alcohol passes from the stomach into the small intestine, where it is rapidly absorbed into the blood and distributed throughout the body. Because it is distributed so quickly and thoroughly the alcohol can affect the central nervous system even in small concentrations. In low concentrations, alcohol reduces inhibitions. As blood alcohol concentration increases, a person's response to stimuli decreases markedly, speech becomes slurred, and he or she becomes unsteady and has trouble walking. With very high concentrations - greater than 0.35 grams/100 milliliters of blood (equivalent to 0.35 grams/210 liters of breath ) - a person can become comatose and die.
The American Medical Association has defined the blood alcohol concentration level of impairment for all people to be 0.04 grams/100 milliliters of blood (equivalent to .04 grams/210 liters of breath).
The following is a generally accepted guide to the affects of alcohol.
| BAC (g/100 ml of blood or g/210 l of breath) | Stage | Clinical symptoms |
|---|---|---|
| 0.01 - 0.05 | Subclinical | Behavior nearly normal by ordinary observation |
| 0.03 - 0.12 | Euphoria | Mild euphoria, sociability, talkativeness Increased self-confidence; decreased inhibitions Diminution of attention, judgment and control Beginning of sensory-motor impairment Loss of efficiency in finer performance tests |
| 0.09 - 0.25 | Excitement | Emotional instability; loss of critical judgment Impairment of perception, memory and comprehension Decreased sensatory response; increased reaction time Reduced visual acuity; peripheral vision and glare recovery Sensory-motor incoordination; impaired balance Drowsiness |
| 0.18 - 0.30 | Confusion | Disorientation, mental confusion; dizziness Exaggerated emotional states Disturbances of vision and of perception of color, form, motion and dimensions Increased pain threshold Increased muscular incoordination; staggering gait; slurred speech Apathy, lethargy |
| 0.25 - 0.40 | Stupor | General inertia; approaching loss of motor functions Markedly decreased response to stimuli Marked muscular incoordination; inability to stand or walk Vomiting; incontinence Impaired consciousness; sleep or stupor |
| 0.35 - 0.50 | Coma | Complete unconsciousness Depressed or abolished reflexes Subnormal body temperature Incontinence Impairment of circulation and respiration Possible death |
| 0.45 + | Death | Death from respiratory arrest |
Absorption
Alcohol is absorbed from all parts of the gastrointestinal tract largely by simple diffusion into the blood. However the small intestine is by far the most efficient region of the gastrointestinal tract for alcohol absorption because of its very large surface area. In a fasting individual, it is generally agreed that 20% to 25% of a dose of alcohol is absorbed from the stomach and 75% to 80% is absorbed from the small intestine. Because of this peak blood alcohol concentrations are achieved in fasting
people within 0.5 to 2.0 hours, while non-fasting people exhibit peak alcohol concentrations within 1.0 to as much as 6.0 hours.
Distribution
Alcohol has a high affinity for water and is therefore found in body tissues and fluids inasmuch as they contain water. Absorbed alcohol is rapidly carried throughout the body in the blood and once absorption of alcohol is complete an equilibrium occurs such that blood at all points in the system contains approximately the same concentration of alcohol.
Elimination
The liver is responsible for the elimination - through metabolism - of 95% of ingested alcohol from the body. The remainder of the alcohol is eliminated through excretion of alcohol in breath, urine, sweat, feces, milk and saliva. The body uses several different metabolic pathways in its oxidation of alcohol to acetaldehyde to acetic acid to carbon dioxide and water.
Healthy people metabolize alcohol at a fairly consistent rate. As a rule of thumb, a person will eliminate one average drink or .5 oz (15 ml) of alcohol per hour. Several factors influence this rate. The rate of elimination tends to be higher when the blood alcohol concentration in the body is very high or very low. Also chronic alcoholics may (depending on liver health) metabolize alcohol at a significantly higher rate than average. Finally, the body's ability to metabolize alcohol quickly tend to diminish with age.
Body Weight and Body Type
In general, the less you weigh the more you will be affected by a given amount of alcohol. As detailed above, alcohol has a high affinity for water. Basically one's blood alcohol concentration is a function of the total amount of alcohol in one's system divided by total body water. So for two individuals with similar body compositions and different weights, the larger individual will achieve lower alcohol concentrations than the smaller one if ingesting the same amount of alcohol. However, for people of the same weight, a well muscled individual will be less affected than someone with a higher percentage of fat since fatty tissue does not contain very much water and will not absorb very much alcohol.
Rate Of Consumption
Blood alcohol concentration depends on the amount of alcohol consumed and the rate at which the user's body metabolizes alcohol. Because the body metabolizes alcohol at a fairly constant rate (somewhat more quickly at higher and lower alcohol concentrations), ingesting alcohol at a rate higher than the rate of elimination results in a cumulative effect and an increasing blood alcohol concentration.