What is paraxanthine, and how is it different from caffeine?

By Gabe Stoddard, founder of Relm. Updated September 28, 2026.

Paraxanthine is the main compound your body makes when it breaks down caffeine, and it acts on the same receptors in your brain that caffeine does. It is also sold on its own as an ingredient, and the small human studies so far suggest it can affect attention and reaction time in ways that look a lot like caffeine, although those studies were mostly paid for by the company that makes it.

Where does paraxanthine come from?

When you drink a coffee, an enzyme in your liver called CYP1A2 does most of the work of breaking the caffeine down. A 2022 review in Frontiers in Pharmacology describes the first step, which turns caffeine into paraxanthine, as the main reaction in caffeine metabolism and puts it at around 80 to 90 percent of caffeine's breakdown. A 2021 study in Nutrients gives a lower figure of about 70 percent of the caffeine you take in, so the exact share depends on how it is measured, but in both cases it is most of it.

That means that for many hours after a coffee, you are carrying around both caffeine and the paraxanthine your body has made from it. If you have read my earlier piece on how long caffeine lasts in your body, this is part of the reason the answer is not simple.

How does paraxanthine work in your brain?

Through the day your brain builds up a chemical called adenosine, and it attaches to receptors that make you feel sleepy. Caffeine sits on those receptors and blocks adenosine from landing, and paraxanthine does the same thing. A 2013 paper in Neuropharmacology, done in rats, describes paraxanthine as a stimulant with a profile broadly similar to caffeine, and it also reports some differences, including a stronger effect on dopamine release in one brain region.

That last part is worth treating carefully. It comes from animal work, and some of the finer details about how paraxanthine differs from caffeine have not been settled, so I would read it as interesting and not as proven in people.

What have studies in people found?

There are only a few human trials, and they are small. Here is what the ones I could read found.

A 2021 trial in Nutrients gave 13 healthy adults a single 200 mg dose of paraxanthine or a placebo. Over six hours, the paraxanthine group made fewer errors on a card sorting task and had faster reaction times on a short-term memory task at the two-hour mark, and no adverse effects were reported.
A second 2021 trial in Nutrients tested 50 mg, 100 mg, and 200 mg in 12 healthy adults, both as a single dose and daily for a week. The authors reported that 100 mg and 200 mg may affect some measures of memory, reasoning, and response time, that the effects were more consistent at the higher doses, and that side effects were not significantly different between treatments.
A 2024 trial in the Journal of the International Society of Sports Nutrition gave 12 trained runners 200 mg of paraxanthine, 200 mg of caffeine, both, or a placebo before a 10 km run. After the run, the paraxanthine group did better on a card sorting test and had faster reaction times than placebo. Caffeine raised how often runners reported a racing heart, shortness of breath, and nervousness, and paraxanthine alone did not.

All three were funded by Ingenious Ingredients, the company that makes the paraxanthine used, and in each paper some of the authors are researchers for that company and hold patents on paraxanthine. I think it is fair to say the evidence is real and also not independent yet. I could not find a human trial paid for by someone with nothing to gain.

Is paraxanthine the same as caffeine?

They are close relatives, and they are not the same molecule. Both are stimulants that work on adenosine receptors, and your body turns one into the other. The trials above suggest paraxanthine may feel different from caffeine to some people, especially around the heart rate and nervousness questions, but those were small studies at 200 mg, and one 10 km run is not much to build a conclusion on.

There are also things nobody has measured yet. The studies I found did not look at sleep in people, and as a stimulant that shares caffeine's mechanism, it makes sense to give it the same respect you would give caffeine when it comes to the time of day. Research so far also does not tell us how long paraxanthine lasts in the body when it is taken directly, since the timing numbers people quote come from caffeine studies.

Where does Relm fit in?

I care a lot about knowing what is in what I take, which is why I wanted to understand this properly before writing about it. Relm has no added caffeine, and its main stimulant is paraxanthine, with every ingredient and its amount printed on the label. It is a dissolvable strip, so there is nothing to drink, and you decide whether to take one or two.

FAQ

Is paraxanthine just caffeine by another name?

No. Paraxanthine is a different molecule that your body makes from caffeine, and the two act on the same receptors. Research in animals suggests they are not identical in every way, though the human evidence on differences is still thin.

Does paraxanthine cause jitters?

In the small trials so far, side effects such as nervousness or a racing heart were infrequent and were not significantly different from placebo, and in the runner study caffeine produced more of them than paraxanthine did. These were healthy young adults in short studies, so how you personally respond may be different.

Is paraxanthine safe?

The human studies I found, which included doses up to 200 mg and one week of daily use, did not report serious side effects. They were small and short and done in healthy adults, so if you are pregnant, breastfeeding, sensitive to caffeine, or have a medical condition, it is worth asking your doctor first.

Can paraxanthine affect sleep?

It has not been studied for sleep in people, as far as I could find. Because it works like caffeine on adenosine receptors, it is sensible to treat it the way you would treat caffeine and to leave plenty of time before bed.

Sources

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