Chapter 11-Caffeine

Caffeine

The world’s most widely used psychoactive stimulant.

Xanthines

A group of alkaloids that include caffeine, theophylline, and theobromine.

Sources of Caffeine

Coffee, tea, chocolate, soft drinks, energy drinks, some over-the-counter medications.

Time Course of Caffeine

Action begins within ~15 minutes; peaks ~1 hour; half-life ~3 to 5 hours (varies).

Mechanism of Action (Caffeine)

Blocks adenosine receptors (antagonist), leading to increased alertness and arousal.

Physiological Effects of Caffeine

Increased heart rate, blood pressure, respiration, diuresis; smooth muscle relaxation in some tissues.

Behavioral Effects of Caffeine

Improved attention, reduced fatigue, enhanced mood (at moderate doses).

Dependence & Withdrawal

Mild physical dependence can develop; withdrawal includes headache, fatigue, irritability, depressed mood.

Caffeinism

A syndrome of excessive caffeine use: restlessness, anxiety, insomnia, tachycardia, GI upset.

Health Concerns (Caffeine)

Potential issues: reproductive effects, cardiovascular risk in susceptible individuals, interference with sleep.

Reproductive Effects

Possible increased risk of miscarriage, low birth weight at high doses.

Cardiovascular Concerns

May provoke arrhythmias or palpitations in sensitive individuals.

Sleep Disruption

Caffeine can reduce sleep quality, delay sleep onset, and reduce total sleep time.

Over-the-Counter Products Containing Caffeine

Certain pain relievers, weight‑loss pills, cold medicines often include caffeine.

Caffeine in Society

Cultural significance (coffeehouses, social rituals), economic impact of coffee industry.

“Safe” Daily Limits for Caffeine

Generally considered up to ~400 mg/day for healthy adults (varies by guideline).

Vulnerable Populations

Children, pregnant individuals, persons with cardiovascular or anxiety disorders.

Synergistic Effects

Combined use with other stimulants (e.g. nicotine) can intensify effects.

Caffeine & Drug Interactions

Caffeine may interact with certain medications (e.g. stimulants, stimulatory antidepressants).

Public Health Implications

Regulation in food and drug products, labeling, public education about safe use.

caffeine content in 2 oz energy shot

200 mg

caffeine content in 8 oz cola

33 mg

caffeine content in 8 oz brewed coffee

96-100 mg

how do caffeine pills help headaches

vasoconstrictor (headaches can be caused by vasodilation)