Caffeine
The world's most widely used stimulant: an adenosine antagonist that boosts alertness and performance.
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Pharmacology
Contents
WHAT IS CAFFEINE?
Detailed overview
Caffeine (1,3,7-trimethylxanthine) is a natural methylxanthine alkaloid found in coffee, tea, cocoa, guarana and many energy drinks, and is the most widely consumed psychoactive substance in the world. As a competitive antagonist of adenosine A1 and A2A receptors it blocks sleep-promoting signals, sustaining alertness, reaction speed and subjective energy. Blockade of A2A receptors in reward regions indirectly elevates dopamine signaling, improving mood and motivation, and the compound also increases norepinephrine release. Its effects on cognitive and physical performance are backed by robust human evidence: the International Society of Sports Nutrition position stand judges it reliably ergogenic at 3-6 mg per kilogram of body weight.
Mechanism
Adenosine A1/A2A antagonist
Half-life
About 3-6 hours in most adults
Legal status
Freely available; WADA Monitoring Program
Receptor profile
- Adenosine A1/A2A receptorsStrong
- Dopamine signaling (indirect, A2A-coupled)Moderate
- Norepinephrine releaseModerate
- GABA-A receptors (high dose only)Weak
Safety
Side effects, stop signs, contraindications
Side effects · 7
- Insomnia or disrupted sleep if dosed too late in the day (due to the half-life)
- Increased heart rate or palpitations, mild rise in blood pressure
- Jitteriness, tremor and anxiety, especially at higher doses
- Withdrawal symptoms on cessation: headache, fatigue, irritability
- Stomach upset, nausea, increased gastric acid, heartburn
- Increased urination (mild diuretic effect)
- Tolerance with regular use, which can lead to dose escalation
Contraindications · 6
- Pregnancy and breastfeeding: intake should be limited (usually <200 mg/day), consult a doctor
- Cardiovascular disease, arrhythmia, uncontrolled hypertension
- Anxiety disorders, panic disorder: the stimulant effect may worsen them
- Additive, potentially dangerous effect when combined with other caffeine or stimulant sources
- CYP1A2-inhibiting drugs (e.g. fluvoxamine, ciprofloxacin) markedly slow its clearance
- Caution needed with reflux, peptic ulcer or severe insomnia
Related Nootropics
Same therapeutic category
Studies
Related research and clinical findings
International society of sports nutrition position stand: caffeine and exercise performance
Guest NS, VanDusseldorp TA, Nelson MT, Grgic J, Schoenfeld BJ, Jenkins NDM
Caffeine and Cognitive Functions in Sports: A Systematic Review and Meta-Analysis
Lorenzo Calvo J, Fei X, Domínguez R, Pareja-Galeano H
The Acute Effects of Caffeinated Black Coffee on Cognition and Mood in Healthy Young and Older Adults
Haskell-Ramsay CF, Jackson PA, Forster JS, Dodd FL, Bowerbank SL, Kennedy DO
Acute Effects of Caffeine Supplementation on Movement Velocity in Resistance Exercise: A Systematic Review and Meta-analysis
Raya-González J, Rendo-Urteaga T, Domínguez R, Castillo D, Rodríguez-Fernández A, Grgic J
Moderate coffee or tea consumption decreased the risk of cognitive disorders: an updated dose-response meta-analysis
Zhu Y, Hu CX, Liu X, Zhu RX, Wang BQ
Caffeine Use in Sport: A Systematic Review and Meta-analysis of Acute Side Effects and Implications for Athlete Health and Safety
Negaresh R, Al-Riyami SAA, Ghahfarrokhi MM, Del Coso J, Karimi Z, Yaghoobi M
FAQ
FAQ
The world's most widely used stimulant: an adenosine antagonist that boosts alertness and performance.
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Structure & chemistry
The information here is strictly for educational and scientific purposes. It does not replace medical advice or clinical consultation, and it does not encourage illegal substance or pharmaceutical use. Data is sourced. When in doubt, consult your doctor.