Q. How does caffeine affect the brain?

A. Caffeine is the most commonly used drug worldwide. It belongs to a class of drugs known as central nervous system (CNS) stimulants, designed to treat fatigue and drowsiness. Caffeine peaks in the blood anywhere from 15 minutes to 2 hours after ingestion. Caffeine is able to cross the blood-brain barrier, and once in the brain it alters brain function. The FDA recommends no more than 400 mg of caffeine per day per adult. Caffeine can interfere with sleep. Its half-life is typically 5-6 hours. If you ingest 200 mg of caffeine at 2pm, 100 mg is still in your system at 7-8 pm. Oral contraceptives and pregnancy double the half-life. Caffeine’s half-life is longer in children than in adults and may be up to 30 hours in a newborn. Caffeine taken after individuals have ingested alcohol does not sober them up or make them fit to drive. It may make them more alert temporarily, but it does not reverse the poor judgment and other effects associated with alcohol.