Being drunk, or experiencing acute alcohol intoxication, is a temporary condition resulting from the consumption of ethanol, the alcohol found in beverages. This state fundamentally affects the central nervous system, which is responsible for controlling thought, movement, and behavior. The presence of alcohol in the body progressively alters a person’s judgment, coordination, and reaction time. Intoxication is a spectrum, and the degree of impairment is directly related to the concentration of alcohol circulating in the bloodstream.
The Body’s Reaction to Alcohol
Ethanol is absorbed into the body rapidly, primarily through the small intestine, though some is absorbed directly from the stomach. Once absorbed, it travels through the bloodstream, easily crossing the blood-brain barrier. Alcohol acts as a central nervous system (CNS) depressant, meaning it slows down activity in the brain and spinal cord.
The depressant effect occurs because ethanol interferes with neurotransmitters, particularly by binding to receptors for Gamma-aminobutyric acid (GABA), the brain’s main inhibitory neurotransmitter. This binding enhances the inhibitory signals, which leads to the sedative effects, cognitive dysfunction, and poor coordination associated with being drunk. Meanwhile, the liver works to metabolize the alcohol, breaking down the ethanol into acetaldehyde and then into acetate.
The primary objective measure of intoxication is the Blood Alcohol Concentration (BAC), which represents the percentage of alcohol in the blood. A BAC of 0.08%, for example, means there are 0.08 grams of alcohol per 100 milliliters of blood. The rate at which BAC rises depends on factors like the speed of consumption, body weight, sex, and the presence of food in the stomach, which can slow absorption.
The Progression of Observable Effects
The experience of drunkenness is characterized by predictable stages of impairment that correlate directly with rising BAC levels. At lower BAC levels, generally between 0.02% and 0.05%, the effects are mild, often described as subclinical intoxication or euphoria. A person may feel relaxed, experience an altered mood, and have slightly lowered inhibitions, becoming more talkative or animated than usual.
As the BAC progresses to the range of 0.06% to 0.15%, the effects become more pronounced, entering the stage of excitement and reduced muscle coordination. Judgment becomes significantly impaired, alongside a noticeable loss of fine motor skills and balance. Speech may become slurred, reaction time slows, and emotions can become exaggerated, sometimes leading to aggressive behavior.
Higher concentrations, specifically between 0.15% and 0.30%, lead to the confusion and stupor stages, where the depressive qualities of alcohol dominate. Physical symptoms include severe loss of balance and muscle control, making it difficult or impossible to stand or walk without staggering. Mental confusion, disorientation, and memory loss, known as blackouts, become increasingly likely as the brain struggles to process information.
At BACs exceeding 0.30%, the body is at risk of alcohol poisoning, a potentially life-threatening condition. Central nervous system depression is so severe that basic functions are compromised, leading to stupor, loss of consciousness, and a high risk of respiratory depression. At these extreme levels, there is danger of coma or death from the respiratory system slowing down completely.
Defining Legal Intoxication
Governments establish specific Blood Alcohol Concentration thresholds to objectively define legal intoxication, primarily concerning the operation of motor vehicles. This regulatory standard allows for consistent enforcement of laws related to impaired driving, known as Driving Under the Influence (DUI) or Driving While Intoxicated (DWI). For adult drivers in all states in the United States, the legal limit is uniformly set at a BAC of 0.08%.
Reaching this 0.08% threshold means a person is legally impaired, regardless of whether they believe they are functioning normally or exhibiting obvious signs of drunkenness. Studies show that at this BAC, a driver’s muscle coordination, judgment, and ability to detect danger are significantly reduced. The 0.08% limit is a regulatory marker for severe legal consequences, including fines, license suspension, and potential jail time.
Specific groups face stricter regulations, such as commercial drivers who often have a lower limit of 0.04%. Zero-tolerance laws for individuals under the legal drinking age of 21 enforce a BAC limit near 0.00%. This ensures that any measurable alcohol level can result in charges for minors.