About Paraxanthine | The Science & Benefits of Px – Rarebird Coffee

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Px is what caffeine isn't

Every bit of energy, focus, and performance.

All without the side-effects.

But what is Px?

First let's address the elephant in the room. It's a lot easier to pronounce than it looks:

pair - uh - zan - theen

Px (short for paraxanthine) is the primary human metabolite of caffeine—a condensed way just to say "the main substance your body turns caffeine into."

In nature, it can be found in very small amounts in some foods, including coffee beans, Theobroma cacao fruits, citrus flowers, and Sicilian orange flower honey. However, it primarily exists inside our bodies while processing caffeine.

Because Px is derived from caffeine, it has many of the same benefits—increased alertness, reduced fatigue, and decreased drowsiness. However, the natural differences between them make Px much less likely than caffeine to cause negative side effects, including “jitters”, anxiety, irritability, and nervousness.

Read our story

Benefits beyond energy

Recent studies (both by Rarebird and by independent researchers) on paraxanthine have shown many potential benefits of Px:

Endurance

In some studies, Px has been shown to boost nitric oxide production, leading to increased treadmill endurance, grip strength, and muscle mass.

Elite Focus

Px has been shown to have cognitive performance benefits and may even help to preserve dopaminergic neurons, helping to protect against age-related cognitive decline.

Better Sleep

Px can improve your sleep quality. In mice, Px showed no evidence of sleep rebound (debt) compared to caffeine, while providing the same amount of wakefulness at equimolar concentrations.

Reduced Stress

In animal and clinical studies, caffeine is anxiogenic (anxiety increasing). In contrast, Px has been shown to exhibit anxiolytic (anxiety decreasing) properties.

Endurance

Elite Focus

Better Sleep

Reduced Stress

AS SEEN IN

Px vs. Caffeine

The energy-boosting effects of caffeine come from it's ability to inhibit Adenosine receptors A1 and A2A.

We measured Px and caffeine head-to-head, and the results speak for themselves: Px is up to 2.7x (A1) and 3.5x (A2A) more effective than caffeine.

This means Px has the ability to provide all the focus, energy, and performance of caffeine—but without the jitters, anxiety, and impact on sleep quality.

Read our story

Is Px Safe?

Paraxanthine has GRAS (Generally Regarded As Safe) status and as compared to caffeine, has a higher oral LD50 (829-1601 mg/kg vs. 127-367 mg/kg for caffeine; rodent) and NOAEL (no adverse effect level)—185-300 mg/kg vs. 150 mg/kg.

Additionally, Px has been shown to have a shorter half-life (3.1 hours) than caffeine (4.1h) and the other major caffeine metabolites, theobromine (7.2h) and theophylline (6.2h), meaning it is processed and cleared from the body faster, so it is less likely to negatively affect sleep quality.

Both paraxanthine and caffeine are CNS stimulants. As such, Px is not intended for use by children and you should consult your physician if you are pregnant, lactating, have a medical condition, or are taking any medications.

Join thousands

Who have experienced the difference

DECAF

ENERGY

SLEEP

HEALTH

TASTE

"I’m pretty sensitive to caffeine (and find the extended half life can interrupt my sleep, even when my last cup is around 1pm), but I’ve noticed a big difference with the Px in Rarebird... Rarebird is now basically the only coffee I drink"

Jeremy

Verified Buyer

"I was a true coffee lover since my teens, but after my 2nd pregnancy things changed & I couldn't handle it anymore. I wasn't able to have coffee anymore because of major jitters & blood sugar crashes, and too frequent bathroom breaks. Sadly I gave it up. Decaf was ok, but it was never as good and I could handle tea caffeine, so I stuck with that. But I can drink Rarebird! It truly doesn't cause any of these problems for me and it really is a miracle. I can finally enjoy coffee, even in the (early) afternoon."

M.S.

Verified Buyer

"Absolute life changer for me, given my sensitivity to caffeine. I’d switched completely to decaf since I’m no longer able to tolerate caffeine, but discovering Rarebird has been a godsend... Dark roast is some of the best coffee I’ve ever had."

Brendan

Verified Buyer

Jeremy

Verified Buyer

M.S.

Verified Buyer

Brendan

Verified Buyer

Jeremy

Verified Buyer

"Love it! 😍 All the benefits of regularly caffeinated coffee without the jitters!"

Paula D.

Verified Buyer

"I almost never write reviews, but this coffee is nothing short of a revelation. It delivers all the amazing perks of caffeine—focus, energy, and clarity—without any of the usual downsides. No crashing. No grogginess the next day. Just pure, clean energy that keeps you in the zone. The paraxanthine infusion has completely transformed my coffee experience, and honestly, my life. It’s become my secret weapon for tackling busy days, and I can’t stop raving about it to everyone I know. This isn’t just coffee—it’s a revolution. I truly believe it’s going to reshape the industry in a way that’s healthier and smarter for all of us."

Ju K.

Verified Buyer

"I’m a slow caffeine metabolizer so I was super happy to find this Px Coffee. I feel focused with no jitters, kinda like I took an adderall. And I have been able to sleep great. If it were regular caffeine id be up all night if I had any past 10am. The flavor is great and works well in my espresso machine."

Michelle R.

Verified Buyer

"I've always been quite sensitive to caffeine, but I also really enjoy drinking coffee. The consequences for [it] were spikes in anxiety and blood pressure. Even still, it seemed like my sensitivity kept getting worse over time, and I eventually... I needed to go caffeine free permanently. It was only a couple months after I made this decision that I found Rarebird... I became a subscriber shortly after trying it. This is the coffee that let me drink coffee again, and I'm really thankful for that. It's great-tasting, high quality coffee too."

Jamin

Verified Buyer

"Love it! 😍 All the benefits of regularly caffeinated coffee without the jitters!"

Paula D.

Verified Buyer

Ju K.

Verified Buyer

Michelle R.

Verified Buyer

Jamin

Verified Buyer

"Tastes good. Not as tired in the afternoon and easy to fall asleep."

Giovanna A.

Verified Buyer

"I used to struggle with sleep and completely eliminated coffee from my diet for more than a year, which was tough but necessary. I wish I'd had Rarebird at that time."

Andrew W.

Wired Magazine

"My sensitivity to caffeine is that I notice a 2nd cup in the afternoon throws off my sleep... I've really enjoyed their Px Coffee. I've only experimented twice... but happy to say no disruption to sleep"

Kevin V.

Verified Buyer

"Tastes amazing and makes me feel more calm... nice to be able to drink later in the day without having to worry about it hurting my sleep."

Kyle B.

Verified Buyer

"Tastes good. Not as tired in the afternoon and easy to fall asleep."

Giovanna A.

Verified Buyer

Andrew W.

Wired Magazine

Kevin V.

Verified Buyer

"Tastes amazing and makes me feel more calm... nice to be able to drink later in the day without having to worry about it hurting my sleep."

Kyle B.

Verified Buyer

"Love this coffee! Smooth, rounded flavor without the hard impact to my stomach and NO JITTERS. Super happy that I discovered Rarebird."

Diana L.

Verified Buyer

"So I’m a coffee drinker. Not more than a cup a day early in the mornings because I have high blood pressure. Other brands I’ve tried increase my blood pressure because of the caffeine content. But since I’ve been drinking this brand of coffee, my pressure went down. 112/76. I’m still taking my blood pressure medicine though. Prior to Rarebird it was 140/85. No jittery, and I sleep like a baby at night time. Thank you to the creator of this coffee. 🙏🙏"

Bola A.

Verified Buyer

"I work in the financial services industry and have depended on coffee / caffeine since 2015 to keep me at 100%. I've tried natural sources of caffeine, tea, energy drinks that promise to be healthy, just water, and even though Coffee has it's draw backs, I've always come back for over a decade. Not anymore. My office just started offering this in the break room. I typically plan my day around caffeine because to avoid experiencing negative side effects (stomach pain, headache, crash), but I wanted to stress test Rarebird and drank 6 cups (2x my daily intake) and all I felt was energy... 10/10 would recommend."

Jeremy J.

Verified Buyer

"Every women over 40 needs to switch to drinking rarebird. Tastes amazing no hormone issues and sleep issues are gone. No more mid afternoon anxiety."

Briana L.

Verified Buyer

"Love this coffee! Smooth, rounded flavor without the hard impact to my stomach and NO JITTERS. Super happy that I discovered Rarebird."

Diana L.

Verified Buyer

Bola A.

Verified Buyer

Jeremy J.

Verified Buyer

"Every women over 40 needs to switch to drinking rarebird. Tastes amazing no hormone issues and sleep issues are gone. No more mid afternoon anxiety."

Briana L.

Verified Buyer

"My wife is like a total snob about coffee and where it’s sourced and... I bought this for her because intimate love and she ended up liking it a lot. Like a-lot-a-lot. Also she says she doesn’t get jitters or caffeine headaches like her usual stuff and she’s about 88% sure she’s not imagining it. But seriously, she can be really pretentious about it (bean quality) and she says it’s actually great."

Stephen K.

Verified Buyer

"It's really wonderful coffee! I have been enjoying it quite a lot. The flavor is incredibly good, and it does give a nice bump of energy without being overwhelming like regular coffee."

Aaron S.

Verified Buyer

"It's really good coffee. These guys have created a fantastic product. If you really love coffee but can't take the caffeine definitely give this a shot. As a caffeine sensitive person, this coffee even at full strength does not give the jitters or a very racy mind. I feel that it also interferes less with sleep, although it probably does have some effect. The taste is bold but balanced, it's really great stuff overall!"

Brian V.

Verified Buyer

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Rarebird's Story

"Like millions, I relied on caffeine to get through the day—until I realized it was a crutch. Instead of giving me energy, it left me anxious and burned out. When I couldn’t find a better alternative, I was forced to make one. Px Coffee was born from a simple idea: energy should work with your body, not against it."

- Jeffrey, Founder & CEO

Try Px Coffee Today →

The Only Px Coffee

Benefits of Px Coffee

Is Px Coffee right for you?

Exceptional Taste

How to brew Px Coffee

Quality Testing & Science

Rated 4.9/5.0 from 345 reviews

Dark Roast | 12 oz. Bag

Our most popular roast. Rich and bold with notes of dark chocolate, toasted marshmallow, and roasted nuts.

60mg Px per serving

Caffeine-like energy without the jitters

No afternoon crashes, sleepless nights

Roasted fresh to order every week

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