Alcohol (ethanol) is a small water-soluble molecule that acts as a central nervous system depressant, the same pharmacological class as benzodiazepines and barbiturates. It crosses the blood-brain barrier within minutes of ingestion and produces its effects by potentiating GABA-A receptors (inhibitory) and inhibiting NMDA glutamate receptors (excitatory). At low doses this presents as relaxation, lowered social inhibition, and mild euphoria. At higher doses it produces sedation, motor and cognitive impairment, and memory disruption.

Ethanol is metabolised in the liver, primarily by alcohol dehydrogenase to acetaldehyde, then by aldehyde dehydrogenase to acetate. Acetaldehyde is the toxic and carcinogenic intermediate responsible for much of alcohol's downstream damage. A standard drink contains roughly 14g of ethanol: a 12oz beer at 5%, a 5oz glass of wine at 12%, or a 1.5oz shot of spirits at 40%.

Deep-dive

Dosage:

• A standard drink is roughly 14g of pure ethanol: a 12oz beer at 5%, a 5oz glass of wine at 12%, or a 1.5oz shot of spirits at 40%
• US dietary guidelines define moderate drinking as up to 2 drinks/day for men and 1 drink/day for women. UK guidelines recommend no more than 14 units/week (around 112g) for both sexes, spread over at least 3 days
• Liver disease risk rises sharply above 40g/day (≈3 drinks) in men and 20g/day (≈1.5 drinks) in women, sustained over years
• Cancer and brain volume signals appear from low intakes (one drink per day or less) with no established threshold below which risk is zero
• Blood pressure rises linearly with intake from the first drink
• Peak BAC is reached 30-90 minutes after ingestion. Food in the stomach slows absorption and lowers peak BAC by approximately 30-50%
• Average elimination rate is roughly 0.015% BAC per hour, or one standard drink per 60-90 minutes
• Binge drinking is defined as 5+ drinks (men) or 4+ drinks (women) in 2 hours, producing BAC ≥0.08%. This pattern carries acute cardiovascular and injury risks distinct from average daily intake
• Drinking within 3-4 hours of bed produces measurable REM suppression and second-half-of-night sleep fragmentation even at low doses
• Women reach BACs 30-40% higher than men from the same weight-adjusted dose. Adjusting intake downward roughly halves the effective dose
• Older adults reach higher BACs from the same dose due to reduced body water and slower clearance

Here's what you can expect:

At one to two drinks (BAC roughly 0.02-0.05%), most people experience relaxation, mild euphoria, and lowered social inhibition within 20-40 minutes. Reaction time and fine motor coordination are measurably impaired even when subjective impairment is mild. Sleep that night will have reduced REM and more fragmented second-half sleep, even if sleep onset feels easier.

At three to four drinks (BAC roughly 0.06-0.10%), there is clear impairment of judgement, motor control, and memory encoding. Heart rate rises, flushing is common. Sleep is significantly disrupted with rebound wakefulness in the early morning hours.