Teacrine

Theacrine's pharmacology appears to overlap with caffeine's but is less well mapped. In rats, Feduccia and colleagues showed that theacrine increases locomotor activity and that this effect involves both adenosine receptors (A1 and A2A, the targets of caffeine) and dopamine D1 and D2 receptors; blocking either system blunted the stimulation. Antagonism of adenosine receptors reduces the brain's sleep-pressure signal and indirectly raises dopamine and noradrenaline release, which is the familiar caffeine mechanism, while the stronger dopaminergic component may explain the 'motivation and mood' emphasis in theacrine marketing. Curiously, an earlier mouse study from China found sedative and hypnotic effects at higher doses, so the compound may be biphasic — stimulant at low doses, calming at high ones — which has not been examined in people. In rodents it also shows anti-inflammatory and analgesic activity. Two pharmacological differences from caffeine matter for users. First, theacrine's elimination half-life in the only human pharmacokinetic study was long — around 20 hours, compared with roughly 5 hours for caffeine — so it accumulates with daily use and can disturb sleep when taken later in the day. Second, co-ingested caffeine increases theacrine's peak concentration and total exposure, apparently by competing for the same metabolic enzymes, so stacking the two amplifies theacrine. The claim that theacrine does not produce tolerance rests on the absence of a declining subjective response over 8 weeks in one study; the adenosine-receptor upregulation that underlies caffeine tolerance has not been studied for theacrine.

The human literature is small, recent and largely funded by the ingredient's manufacturer. Habowski and colleagues reported in a 2014 conference abstract that a single 200 mg dose of TeaCrine improved subjective energy, focus and concentration without changing heart rate or blood pressure. Ziegenfuss and co-workers extended this in a two-part 2017 study: an acute 200 mg dose produced no change in oxygen consumption, heart rate or blood pressure, and participants reported improved energy and reduced fatigue versus placebo. The main safety trial, by Taylor and colleagues in 2016, randomized 60 healthy adults to 200 mg or 300 mg of TeaCrine daily or placebo for 8 weeks and found no clinically relevant changes in heart rate, blood pressure, blood lipids or liver and kidney chemistry, and no evidence that subjective effects faded over the period — the basis of the 'non-habituating' claim. Cognitive and performance results are mixed. Kuhman and colleagues in 2015 compared a theacrine-containing product, caffeine and placebo in young adults and found no meaningful differences in cognitive performance, with some subjective improvements. Bello and colleagues in 2019 gave 24 high-level soccer players TeaCrine (275 mg), caffeine (275 mg), a combination (125 mg theacrine plus 150 mg caffeine) or placebo before a simulated match; the theacrine and combination conditions better maintained reaction time and endurance performance late in the match than placebo, while caffeine alone did not reach significance on all measures. By contrast, Cesareo and colleagues in 2019 found that neither TeaCrine nor caffeine improved muscular strength, endurance or power in resistance-trained men. He and colleagues in 2017 characterized the pharmacokinetics and showed that caffeine increases theacrine exposure. Methylliberine (Dynamine) has a similarly small set of acute and short-term safety studies. Taken together, the evidence supports theacrine as a mild, well-tolerated stimulant over the short term in healthy young adults; it does not establish superior performance versus caffeine, does not prove absence of tolerance beyond 8 weeks, and provides no data in people with cardiovascular disease, in older adults or over long-term daily use.

Theacrine (1,3,7,9-tetramethyluric acid), a methyluric acid one step removed from caffeine in structure; branded TeaCrine is synthetic 'nature-identical' theacrine; in nature it occurs with caffeine and theobromine in the leaves of kucha tea (Camellia assamica var. kucha) and in cupuaçu (Theobroma grandiflorum) seeds

Theacrine is well absorbed by mouth, with blood levels peaking within a couple of hours and effects reported within 30–60 minutes; its elimination half-life of about 20 hours in the single human pharmacokinetic study is roughly four times that of caffeine, so a daily dose builds to a steady state over several days and a late-afternoon dose can still be at meaningful levels at bedtime. Caffeine taken alongside raises theacrine's peak and total exposure, probably by competing for hepatic metabolism, which is why stacked products use lower theacrine amounts. Because the branded ingredient is synthetic and chemically identical to the plant alkaloid, the 'natural' versus 'nature-identical' distinction has no bearing on absorption. The enzymes that clear theacrine have not been definitively identified in humans.

• Kucha tea leaves (Camellia assamica var. kucha) from Yunnan — the only dietary source with meaningful amounts
• Cupuaçu (Theobroma grandiflorum) seeds, in small quantities
• Not present in ordinary green, black or oolong tea, coffee or cocoa