RESEARCH MONOGRAPH · KDC-MN-162

Caffeine

May 9, 2026 Kodiac biolabs Research Revised May 30, 2026 2 min read

Our opinion on this compound

91/100

The most-studied psychoactive on earth and somehow people still get the basics wrong

Caffeine is the only compound on this list that's been consumed at scale for centuries, characterized down to the crystal structure for over a century, and we still see supplement marketing that gets the pharmacology backwards. So a few honest takes.

Mechanism is well-mapped: competitive antagonism at adenosine A1 and A2A receptors, which is why the alertness effect tracks with adenosine accumulation through the day. There's also weak phosphodiesterase inhibition and calcium release effects at very high doses, but those are not relevant at typical research exposures. The A2A antagonism in striatum is what couples caffeine to dopamine signaling indirectly, which is why dopaminergic genes (and Parkinson's risk) modulate the response.

Pharmacogenomics matters more than people think. CYP1A2 metabolism varies maybe 10-fold between fast and slow metabolizers. Fast metabolizers (homozygous AA) clear caffeine in 2-4 hours and tolerate higher exposures with cardiovascular benefit. Slow metabolizers (C-allele carriers) clear it in 8+ hours, and there's a real signal in epidemiology that they have worse cardiovascular outcomes at high intakes. The same molecule, two different drugs depending on your CYP1A2 genotype.

Tolerance is real and develops in 1-2 weeks for the alertness effect via A1/A2A upregulation. The performance effects (endurance, force production) tolerize less, which is why caffeine still works as an ergogenic aid even in habituated users.

Sourcing is trivial. Anhydrous caffeine is a commodity, pharmacopoeia-grade material is cheap and clean, HPLC is unnecessary in practice because the synthesis is so well-established. Caffeine citrate (used in neonatal apnea) is the slightly different salt form, more soluble.

What we like: it's the cleanest, best-characterized adenosine antagonist we have, and decades of epidemiology consistently show mortality, neurodegeneration, and liver outcomes pointing the right direction at moderate exposures. What we dont like: the supplement-stack marketing that loads 300mg+ into pre-workout blends without disclosing genotype variability, and the entire pulverized-anhydrous-caffeine market that has actually killed people via overdose because there's no safe consumer way to weigh sub-100mg of fluffy white powder.

Take it seriously as a pharmacological tool, not as a beverage additive.

Evidence: 95
Mechanism: 92
Reliability: 90
Safety: 78
Sourcing: 95
Value: 95
Signal: 88
Staying power: 95

Plain-language summary Intrigue 65 / 100

Caffeine is the world's most widely consumed psychoactive substance. It blocks adenosine receptors that normally promote sleep, producing alertness and reduced fatigue. The half-life of about 5 hours means that an afternoon coffee can disrupt nighttime sleep. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Methylxanthine adenosine receptor antagonist

The world's most consumed psychoactive substance, an adenosine receptor antagonist with widespread cognitive and physical performance effects.

Abstract

Caffeine (1,3,7-trimethylxanthine; CAS 58-08-2; molecular formula C8H10N4O2; molecular weight 194.19) is the most widely consumed psychoactive substance in the world, present in coffee, tea, cocoa, and many caffeinated beverages and dietary supplements. Mechanism is non-selective adenosine receptor antagonism (A1, A2A, A2B, A3) at typical dietary doses, with secondary inhibition of phosphodiesterase and modulation of GABA-A receptors at supratherapeutic concentrations. The adenosine A2A receptor antagonism is the principal driver of cognitive and motor effects. Pharmacokinetics: plasma half-life 3 to 5 hours; CYP1A2 metabolism (variable by genotype); renal excretion of metabolites. Reported research dose ranges in the literature for performance applications span 100 to 400 mg; tolerance develops within 1 to 2 weeks of regular use.

Mechanism of action

Non-selective adenosine receptor antagonist (A1, A2A, A2B, A3). PDE inhibition at higher doses.

Reported research dose ranges

Reported research dose ranges in the literature span 100 to 400 mg; tolerance develops with regular use.

References

Fredholm BB, et al. Adenosine, an endogenous distress signal, modulates tissue damage and repair. Pharmacol Rev 1999.

Read the full monograph

Available as a research-use-only PDF download. Note: PDFs for newly added compounds may take a few hours to propagate after this article was published.

KDC-MN-162

The full reference document is provided strictly for research use only. It reports research dose ranges from the published literature, not instructions for use in humans or animals.

Download PDF →

FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

Kodiac sells research compounds for investigative use only.

Caffeine

Abstract

Mechanism of action

Reported research dose ranges

References

Read the full monograph

Quick actions

Categories

Help and policies

Abstract

Mechanism of action

Reported research dose ranges

References

Read the full monograph

Adjacent monographs