Caffeine vs Alcohol

What the chemistry adds up to:

• Caffeine holds off sleepiness by occupying adenosine receptors — it borrows alertness rather than creating energy
• Tolerance can involve adenosine-system adaptation, but researchers do not reduce it to one settled receptor-count mechanism
• Alcohol dials brain activity down by lifting GABA and muting glutamate
• Mixing the two is risky: caffeine hides alcohol's sedation, so you feel more sober than you are
• Hangovers trace back to acetaldehyde, dehydration, and inflammation