Orexin B: The Definitive Guide

What is Orexin B?

Orexin B is a natural signalling peptide made by a small cluster of nerve cells in the hypothalamus, the part of the brain that manages sleep, appetite and body states. It is one of two orexin peptides that help hold the brain in a stable waking state. People search for it because of narcolepsy, because of the new orexin medicines, and because it is sold online next to its better-known sister, Orexin A.

Two research teams described the pair in 1998 and gave them two sets of names. One team called them orexin-A and orexin-B, found that both are cut from the same parent protein, and showed that both made rats eat more when given into the brain. [1] The other called them hypocretin-1 and hypocretin-2, because they come from the hypothalamus and resemble the gut hormone secretin. [2] Orexin B and hypocretin-2 are the same molecule. Other labels you will see are OXB, OxB, Hcrt-2 and HCRT2.

Chemically it is a straight chain of 28 amino acids: RSGPPGLQGRLQRLLQASGNHAAGILTM, with the last amino acid capped (an "amide"). [4] Its formula is C123H212N44O35S and its molar mass about 2,899 g/mol. [5] Unlike Orexin A, it has no disulfide bridges holding it in shape. The structure studies disagree on its shape in water: one NMR study found two short coils (helices) joined by a linker even in water, while a circular dichroism study found it unordered in water and coiled in a membrane-like environment. [6], [7] A membrane-mimicking study also found two helical sections. [4] Both peptides come from one parent protein, prepro-orexin, so one gene makes both. [3]

Products sold as Orexin B are made in a laboratory. They are 1 mg or 5 mg vials of freeze-dried powder labelled for research, and the sellers state they are not for human use. [52], [53], [54] It is not an approved medicine anywhere (see legal status), and it has its own guide separate from Orexin A because the two behave differently (see the comparison).

Typical Orexin B Protocols

Two of the three websites that state an orexin B amount give 50–100 mcg a day; the nasal page gives 100–200 mcg when needed. No study, label or registered trial stands behind any of them. [62], [63], [64]

Titration Changing the amount in steps

One calculator page starts at 50 mcg once a day and moves to 100 mcg once a day, with 250 mcg a day listed as a higher alternative. The other pages give no starting step. [63]

Breaks and cycles

One post describes use only when needed or in 2–4 week cycles, without saying how long to pause between them. The nasal page describes use only when needed. No source links a break to any measured effect. [62], [64]

Read the units: these amounts are in micrograms (mcg); 1 mg equals 1,000 mcg, so a 5 mg vial holds 5,000 mcg. On an insulin syringe, units measure volume, not an amount of orexin B. As arithmetic only: a 5 mg vial mixed with 2 mL of liquid holds 2.5 mg per mL (25 mcg per unit on a U-100 syringe), so 100 mcg is 0.04 mL, or 4 units. [63] Doserly's reconstitution calculator works this out for any vial. Research papers instead give orexin B in nanomoles (a count of molecules): with a molar mass of about 2,899 g/mol, 1 nmol weighs about 2.9 mcg, so 100 nmol is about 290 mcg (0.29 mg). [5]

Each row is one website's schedule as published, and low, mid and high are alternatives, not steps to move through. These numbers come from websites rather than studies: the pages themselves call them community practice or lab examples, and none cites a human study. [62], [63] (See where the website numbers come from.)

What amounts do sites give for nasal sprays?

The nasal page states its number is "community practice rather than a trial result". [62] Nothing shows how much orexin B, if any, reaches the brain through the nose (see routes). A third chart site lists the route as subcutaneous and gives no amount. [65]

Nothing else supplies a human dose. No published study and no ClinicalTrials.gov record has given orexin B to a person; the registry's orexin-related records are receptor-drug and measurement studies. No orexin B medicine exists in the United States or Canada, so there is no label to follow. A 2025 self-experiment proposal reserved pure nasal orexin B for its highest funding level; the group later tested orexin A only, and no orexin B amount or result has been posted. [42], [43], [50], [56], [70] Every other orexin B amount comes from animals or tissue in a dish, and amounts per kilogram in animals are never scaled to people (see the animal amounts).

Three cautions matter more than any of these numbers.

Serious daytime sleepiness needs a diagnosis, not a research vial. Falling asleep without warning, or sudden muscle weakness when you laugh or feel strong emotion (cataplexy), can point to narcolepsy. A diagnosis opens up approved treatments, including, in the United States since August 2026, a tablet for narcolepsy type 1 that switches on the same receptor orexin B prefers. [40], [41]

An injection may never reach the brain. In mice, orexin B injected into a vein was broken down in the blood, and none arrived in the brain intact. [10] In sheep, an intravenous dose had no effect on eating, while orexin given straight into the brain did. [12] Whatever the effect of an injected research vial, the evidence says it is unlikely to be the brain effect people buy it for, while the risks of an unregulated injection remain.

The side effects of the approved relative are the best warning available. On the approved tablet, insomnia affected 55% to 60% of patients depending on dose, against 1% on placebo; frequent urination, blood-pressure and cholesterol rises were also more common than on placebo; and an earlier drug of the same kind was stopped because of liver injury. [39], [40] Those are different molecules. They show what switching on this receptor for days at a time can do in people, and orexin B has never been tested at all.

What is Orexin B commonly used for?

Orexin B is discussed for three things: staying awake or needing less sleep, narcolepsy, and a spread of laboratory ideas such as appetite, brain protection and pain. None of these is an approved use, and none has been tested in people. Everything below comes from animal studies, cell studies, or measurements of the body's own orexin B.

The appeal is easy to see. Orexin keeps the brain's waking state steady, most people with narcolepsy type 1 have lost the cells that make it, and orexin B prefers the receptor most linked to sleep and wakefulness. [8], [14], [17], [19] The problem is getting a peptide from a vial to the right brain cells, and for orexin B the mouse evidence says the bloodstream destroys it first. [10]

Staying awake and needing less sleep

This is what most online interest is about, and there is no study of it. No human has been given orexin B to test alertness, sleep or sleep need. [50] The only relevant public plan, a 2025 self-experiment proposal, chose to test orexin A first and reserved pure orexin B for its highest funding tier (the lowest tier would have bought an A+B blend) because of its poor passage into the brain and lower potency. [56] The group later ran the trial with orexin A only and reported no significant effect (see the Orexin A guide); no orexin B arm has been reported. [70] In online discussions, one commenter who used an "Orexin A/B" blend described orexin B as "much more stimulation" than orexin A, a personal impression from a blend that cannot be credited to either peptide. [57]

Narcolepsy and cataplexy

Here the research is real but indirect. In mice bred without orexin, a modified orexin B that acts almost only on the OX2 receptor, given straight into the fluid spaces of the brain, reduced cataplexy-like attacks and broken-up waking as well as orexin A did. [14] In separate tests in normal mice, orexin A, which also works on the OX1 receptor, triggered drug-seeking behaviour, and the modified orexin B did not. [14] Findings like this are the biological case for OX2 receptor drugs such as oveporexton, the approved narcolepsy tablet, which is a small manufactured molecule and not orexin B. [17], [18], [40]

Appetite and weight

The name orexin comes from feeding research: given into the brain, both orexins made rats eat more. [1] Outside the brain the results split. A single 3 mg per kg injection into the muscle of young pigs raised their 24-hour feed intake by 18%, while an intravenous dose of 3 mcg per kg in sheep did nothing. [12], [13] In human fat tissue in a dish, orexin B switched on a gene involved in fat-cell development. [25] Nothing here supports orexin B for weight loss or weight gain in people.

Brain protection, pain and other laboratory ideas

Several research lines get quoted as if they were benefits. In dishes of rat brain cells, orexin B protected dying dopamine neurons, the cells lost in Parkinson's disease, while orexin A barely did; in mice poisoned with a Parkinson's-inducing chemical, orexin B into the brain reduced the loss of those cells and improved movement. [26], [27], [28] In mice given daily orexin B injections from the day after aneurysm-inducing surgery, brain-artery aneurysms were smaller than in untreated mice (1.93 against 3.72 mm, 6 mice per group), but not in mice lacking OX2; it also reduced deaths and lung injury in a sepsis model. In rats, it eased nerve pain and improved a learning task. [24], [29], [30], [31] Other mouse studies found the opposite for head pain: orexin B applied to the brain's outer lining triggered migraine-like pain in male mice, and it made pain-sensing nerve cells from male mice, monkeys and people more sensitive. [67], [68] In dishes, it triggered the death of colon-cancer and nerve-tumour cells but not normal gut cells. [34], [35] Each is a result in one specific model, mostly from single laboratories, and none has been tested in a person.

See what has been measured in people or how it might work.

Where do Orexin B protocols differ?

No study has tested any human schedule, so the disagreements are about where the website numbers come from, units and product identity. Here is what varies, and why each point matters.

Where do the website amounts come from?

Three websites give human amounts, and they do not agree on route, amount or schedule. [62], [63], [64]

• No human study behind them. The nasal page links its amount to a 1998 animal study and then states that the study "shows the mechanism, not a human dose". [62] The calculator page labels its amounts as lab examples and says no human injectable dose is established. [63] The cheat-sheet post gives no source for its numbers. [64]
• Errors on the pages. The nasal page labels orexin B as "studied in humans" and describes it as containing disulfide bonds. No study has given it to a person, and orexin B is a straight chain with no disulfide bridges. [4], [50], [62] It also states a 1 to 3 hour duration of action that no study measured (see how long it lasts).
• Selling links and claims. The cheat-sheet post links its orexin B entry to a seller with a referral code and describes orexin B as an "alternative to stimulants" with "no jitters". [64] No study supports either claim.
• Route does not change the number. The cheat-sheet post gives the same 50–100 mcg for injection and nasal spray, although the two routes would deliver very different amounts to the body, and neither has been measured. [64]

What amounts appear in animal research?

These are published orexin B amounts in animals and dishes, listed so readers can see them in context. They are not human doses, they are not scaled to people, and several were single experiments.

The pig amount is roughly a thousand times the sheep amount per kilogram, and the routes differ. Two studies that injected orexin B outside the brain reported effects: pig feeding (into a muscle) and smaller mouse aneurysms (into the belly cavity, a blood-vessel effect rather than a brain effect). [12], [13], [24] That is why these rows cannot be turned into a human range.

Nanomoles or micrograms?

Research papers usually count molecules in nanomoles; vials are sold by weight in milligrams. For orexin B, 1 nmol is about 2.9 mcg. [5] Orexin A is a longer, heavier chain, so the same number of nanomoles of the two peptides weighs a different amount, and a conversion copied from an Orexin A page will be off. [3] Anyone converting between units by hand can also slip by a factor of a thousand between micrograms and milligrams.

Does an injection even reach the brain?

This is the central problem, and the evidence points one way.

• Broken down in blood. In mice, radiolabelled orexin B injected into a vein was degraded so fast that no intact orexin B could be detected in the brain. Orexin A in the same study crossed in, mostly intact. [10]
• Poor fat solubility. Crossing the blood-brain barrier by simple diffusion depends on being able to dissolve in fat. On a standard oil-and-water test, orexin B scored 0.030 against 0.232 for orexin A, roughly eight times lower. [10]
• No transport system. Researchers found no dedicated carrier that ferries orexin B from blood into the brain. [11]
• No effect from the bloodstream in sheep. An intravenous dose had no effect on eating, while orexin given into the brain did. [12]

Two injected-outside-the-brain studies reported effects: pig feeding after a very large intramuscular dose, where the study did not show where in the body it acted, and smaller mouse aneurysms after daily injections into the belly cavity, a blood-vessel effect rather than a brain effect. [13], [24] No study has tested nasal orexin B in any species, so the nose-to-brain route that researchers have studied for orexin A is untested for orexin B. [69]

Which peptide is in the vial?

Several things can go wrong between the label and the contents.

• A/B blends. Some nasal sprays have been sold as "Orexin A/B" mixtures. [56], [57] In a blend no one can tell which peptide did anything, and there is no evidence that the orexin B part reaches the brain. [10]
• Wrong sequence on a listing. One UK research listing prints two different sequences, a nine-amino-acid one and a 28-amino-acid one ending in the wrong amino acid, and neither matches orexin B or the listing's own formula. [4], [52] A label error like that says nothing definite about what is in the vial, but it shows how little checking these listings get.
• An oxidation-prone peptide. Under oxidizing conditions, the last amino acid (a methionine) oxidizes and another building block changes chemically. [7] That last amino acid and its cap are essential: changing the final five building blocks sharply cuts orexin B's activity at both receptors. [4] A poorly stored vial may contain less working peptide than its label states.

Is orexin B the "stimulating" orexin?

Online, orexin B is sometimes described as the more stimulating of the two, and a thread comparing them drew exactly that claim from someone using a blend. [57] The laboratory picture is more specific. Orexin B works through the OX2 receptor that drives wakefulness in mice, but it is also the one that is destroyed in blood and lacks evidence of reaching the brain from outside it. [10], [14] A felt difference from a blend spray cannot settle which peptide, if either, caused it.

What happens when you stop Orexin B?

Nothing has been studied, because no person has been given it. [50] There are no withdrawal, rebound or recovery data for orexin B in any species.

The nearest evidence comes from the approved OX2 receptor tablet. Its label reports that 277 patients who completed or stopped treatment in repeat-dose studies were monitored after stopping, with limited evidence of withdrawal-related side effects. [40] The same label notes a potential for abuse, higher drug-liking scores than placebo in an abuse-potential study, and a controlled-substance schedule that was still pending. [40] That is a different molecule taken by mouth twice a day, so none of this is a finding about orexin B.

Do injected, nasal and oral Orexin B behave the same way?

No route has been tested in people, so this section is about what animal studies and basic chemistry show. [50]

Intravenous (into a vein) is the route with the clearest animal data, and it is unfavourable. In mice, orexin B was broken down in blood before any intact peptide reached the brain; in sheep, an intravenous dose did nothing to appetite. [10], [12]

Subcutaneous (into the fatty layer under the skin) has never been tested with orexin B in any published study. A subcutaneous dose would have to pass into the bloodstream first, where the mouse data show it is degraded. [10]

Intramuscular (into a muscle) was used once, in young pigs, at 3 mg per kg, and raised feed intake. [13] That dose is enormous by peptide standards, and the study did not show where in the body it acted.

Intranasal (sprayed into the nose) has no orexin B study in any species. Researchers have studied the nose for orexin A because, in rats, nasal nerves offered a partial shortcut to the brain, but that work cannot be transferred to a different peptide with different chemistry. [69] One 2025 self-experiment proposal described its planned nasal orexin B use as among the first in humans, and no result has been posted. [56]

Oral (swallowed) is not a realistic route for a peptide: digestive enzymes break peptides apart. The approved orexin medicine works by mouth because it is a small manufactured molecule, not a peptide. [40]

Into the brain's fluid spaces is how nearly every positive animal result was produced, through a surgically placed tube. [12], [14], [27] It is a research technique, not something a person can do, and it is the main reason animal results do not translate into a usable product.

Doserly

Which routes have been tested for orexin B?

No route has been tested in people. What each route has been tested for in animals. Animal research.

Into a vein · never tested in people

In animals: Mice, sheepWhat happened: Broken down in mouse blood, no intact peptide detected in the brain; no effect on eating in sheep

Under the skin · never tested in people

In animals: No published studyWhat happened: Not tested in any species

Into a muscle · never tested in people

In animals: Young pigs, 3 mg/kg onceWhat happened: Feed intake up 18% over 24 hours

Nasal spray · never tested in people

In animals: No study in any speciesWhat happened: Not tested

Swallowed · never tested in people

In animals: No studyWhat happened: Not tested; peptides are generally digested

Into the brain's fluid · never tested in people

In animals: Rats, mice, sheep (surgical research technique)What happened: More eating, fewer cataplexy-like attacks (modified orexin B), dopamine-cell protection

Almost every positive brain-related result came from delivery straight into the brain. Into a vein it failed in mice and sheep; belly-cavity injections made mouse aneurysms smaller.

How long does it last in the body?

Nobody knows. No measured half-life for orexin B, in people or animals, was found in the studies reviewed. What is known is that it was rapidly degraded in mouse blood. [10] For comparison, the approved OX2 receptor tablet has a half-life of about 23 hours. [40]

How should Orexin B be stored, and how long does it last?

There is no stability study for any orexin B product, so the facts are limited.

• Powder. A research seller says to keep the sealed freeze-dried vial at −20 °C (−4 °F), protected from light and moisture, and to let it reach room temperature before opening so that water does not condense inside. [52] That is a seller's instruction, not a tested shelf life.
• After mixing. No stability study exists for dissolved orexin B. Two seller pages say to keep mixed vials at 2–8 °C (36–46 °F) and use them within about 28 days, and one claims a 2-year shelf life for unopened powder; these are seller statements, not tested data. [52], [63] Sellers also disagree on the powder: one says −20 °C, another just says to refrigerate. [52], [62]
• Why it matters. Orexin B's last amino acid oxidizes under stress, and that part of the molecule is essential for activity. [4], [7] Heat, light, air and repeated handling are all ways to lose working peptide before anyone uses it.

For comparison, the approved OX2 receptor tablet is stored at 20 to 25 °C (68 to 77 °F), because a small manufactured molecule is far more stable than a peptide. [40]

What do we actually know about Orexin B in people?

Very little, and none of it involves giving orexin B to anyone. There is no human dosing study, no case report and no registered trial. [50] Human research on orexin B consists of measurements of the body's own peptide in spinal fluid and blood, and experiments on human tissue in a dish.

What the spinal-fluid studies show

Three studies have used mass spectrometry, a method that identifies molecules by their exact weight, and they disagree.

• Detected and reduced in narcolepsy. A 2025 preprint (not yet peer reviewed) measured active orexin A and orexin B and their broken-down fragments in cerebrospinal fluid. All orexin forms were lower in narcolepsy type 1 than in narcolepsy type 2 or idiopathic hypersomnia, the ratio of short to long orexin B pieces separated those two conditions, and orexin turnover increased during sleep deprivation. [20]
• Not detected at all. A 2026 study with a method sensitive to 0.1 pg/mL found orexin B below that limit in paired spinal-fluid and blood samples from people with narcolepsy and controls, and concluded that spinal-fluid orexin A remains the most reliable clinical marker. [21] An earlier 2021 method, sensitive to 35 pg/mL, also found orexin B undetectable in spinal fluid from 72 people with and without narcolepsy. [61]

The methods differ, and the conflict is unresolved. What both support is that orexin A, not orexin B, is the peptide measured in clinical narcolepsy testing. [21]

Why blood tests for orexin B are not reliable

Several studies, mostly using antibody-based kits, have reported blood orexin B levels: higher in depression (97 patients against 51 controls), unchanged in obesity (36 obese and 16 lean women), and lower in people with brain aneurysms (3.21 against 8.56 pg/mL). [22], [23], [24] The 2026 mass-spectrometry study found orexin B in blood below 0.1 pg/mL in every sample and called previously reported nanogram-level blood orexin readings analytical artefacts. [21] Until methods agree, an orexin B blood result from a commercial kit should not be treated as a meaningful test.

Human tissue in a dish

In human fat tissue, orexin B at 100 nM for 24 hours raised the activity of a gene involved in fat-cell development. [25] In human heart samples, orexin B switched on a cell signalling pathway, and in heart tissue from 54 bypass-surgery patients, lower OX2 receptor levels went with a worse heart-failure symptom class. [9] These are tissue findings and a correlation, not effects of a dose on a person.

What the human data do not include

• No dose of any size, by any route, in anyone. [50]
• No safety data, side-effect reports or case reports of harm. [50]
• No measured half-life, absorption or brain exposure in people.
• No study of orexin B in healthy people for sleep, alertness or mood, and no published self-experiment result. [56]

How might Orexin B work?

The orexin system is well mapped, even though orexin B as a product is not. Both orexins act on two receptors on nerve cells, called OX1R and OX2R. [1] What sets orexin B apart is which of the two it prefers.

It prefers the OX2 receptor. In the binding measurements from the 1998 discovery work, orexin A and orexin B bound the OX2 receptor equally well (half-maximal values of 38 and 36 nM), while orexin B bound the OX1 receptor about 20 times more weakly than orexin A (420 against 20 nM). [8], [9] Some database entries shorten this to "OX2 only", but the measured OX1 activity is real, just weak, so "prefers OX2" is the accurate description. [3], [8]

Lower numbers mean tighter binding. Values from the 1998 discovery work as cited in two later papers, because the original full text was not available for review. [1], [8], [9]

The OX2 receptor is the sleep-wake receptor. Researchers at the company behind the approved medicine describe the OX1 receptor as involved in reward seeking and the OX2 receptor as central to sleep and wake regulation. [17] Most people with narcolepsy type 1 have lost their orexin-making cells. [14], [19] In mice whose orexin cells had been destroyed, orexin A given into the brain suppressed cataplexy-like attacks and increased waking for about three hours. [19] In mice bred without orexin, an OX2-selective orexin B reduced cataplexy-like attacks; in separate tests in normal mice it did not cause the drug-seeking that orexin A caused. [14] That is the biological case for the OX2 receptor drugs that now exist. [18]

Its shape matters at the tail end. The final part of the chain carries most of its activity: the shortest fully active fragment runs from the sixth to the last amino acid, and changing the final five sharply reduces its power at both receptors. [4], [16] Swapping two amino acids produces a research version that is 400 to 1,000 times more selective for OX2. [14], [15] Scientists have also built light-switchable versions to turn the signal on and off with precise timing in cells and zebrafish. [37], [38] These are laboratory tools, not products.

It excites nerve cells. In rat spinal-cord slices, orexin B made pain-processing nerve cells more active through the OX2 receptor. [32] In male mice, orexin B applied to the brain's outer lining made head-pain nerve cells more excitable and triggered migraine-like pain, an effect not seen in females. [67], [68] In isolated newborn-rat brainstem preparations, it counteracted breathing suppression from sevoflurane (at 0.5 micromolar), propofol and a low concentration of remifentanil, but not from a higher remifentanil concentration. [33] In rats, its effect on memory was blocked by an OX2 receptor blocker. [31]

Its reach extends beyond the brain. Human fat tissue and heart tissue carry orexin receptors, and orexin B protected rat hearts after an interruption of blood flow in a laboratory model. [9], [25] In dishes, orexins triggered the death of certain cancer cells through either receptor. [34], [35]

What are the risks and unanswered questions?

Is Orexin B safe?

Its safety in people is unknown, because no one has been given it in a study. [50] There is no safety study, no side-effect report and no case report of harm. An absence of reports for a substance that has never been studied says nothing about safety.

What can be said comes from drugs that switch on the same receptor, and it is worth knowing because it shows what the orexin 2 pathway does in people. These are small manufactured molecules taken by mouth, so the findings are about them, not about orexin B:

• Oveporexton (approved in 2026). In two 12-week phase 3 trials in narcolepsy type 1, insomnia occurred in 55% to 60% of treated patients depending on dose against 1% on placebo, and frequent urination in 53% to 58% depending on dose against 5% on placebo. Rises in systolic blood pressure of more than 20 mm Hg occurred in 22% against 13% on placebo, heart-rate rises of more than 15 beats per minute in 30% against 22%, and LDL cholesterol above 160 mg/dL in 32% against 20%. Muscle-enzyme (creatine phosphokinase) rises above five times normal occurred in 11% against 5%. [40]
• TAK-994 (development stopped). A phase 2 trial in 73 people with narcolepsy type 1 improved sleepiness and cataplexy but was stopped early because of liver problems; 3 patients had drug-induced liver injury meeting a standard severity definition. [39]

Orexin B has never been checked for any of these effects, at any dose. Animal work adds one possible harm signal of its own: in male mice, orexin B applied to the brain's outer lining triggered migraine-like pain, and it made pain-sensing nerve cells from male mice, monkeys and people more sensitive. [67], [68]

What problems have actually been reported?

None specific to orexin B. The only public first-hand account of side effects comes from a person who said that "different Orexins" made them dizzy, without naming which peptide, product or amount. [57] Nobody in the public threads reviewed had their product tested.

Could product quality change the risk?

Yes, and for orexin B this may be the largest practical risk. Research vials are not medicines: no one checks them for sterility, correct content or contaminants on your behalf, and sellers state that they are not for human use. [52], [54] One listing prints a sequence that is not orexin B's. [52] Health Canada warns that unauthorized peptide products may contain too much, too little or none of the stated ingredient, may contain unlisted ingredients or contaminants, and may be improperly made or stored. [46] A peptide that oxidizes easily adds another way for a vial to contain less than its label says. [7]

Is Orexin B legal? Is it FDA-approved?

Checked September 26, 2026. Rules differ by country and change quickly. A "research use only" label does not make a product legal to sell or safe to use.

United States. Orexin B is not an approved medicine, and the FDA's substance database has no entry for it. [42] It is not among the substances nominated for pharmacy compounding under section 503A (list updated May 14, 2026), and it is not on the FDA's list of compounding substances that may pose significant safety risks (content current April 22, 2026). [44], [45] Neither absence is a ruling that selling it is legal. Sellers offer it as research material. [52], [54]

United States, the approved relative. Oveporexton (brand name Orzeyful), a tablet that switches on the orexin 2 receptor, was approved on August 5, 2026 for narcolepsy type 1 in adults under application NDA 220860. Its label records that its controlled-substance schedule was still pending. It is not orexin B. [40], [41]

Canada. Health Canada's Drug Product Database returns no product with orexin or hypocretin as an ingredient. [43] Health Canada's April 2026 advisory warns that unauthorized peptide products are illegal in Canada and have not been assessed for safety, efficacy and quality. [46]

Australia. The Therapeutic Goods Administration's April 2026 guidance on unapproved peptide products does not name orexin B. It states that such products "have not been evaluated for safety, quality or effectiveness by the TGA". [47] The June 2026 Poisons Standard, which lists the medicines and chemicals Australia schedules, does not mention orexin or hypocretin. [66] Not being listed there is not a ruling that selling or importing orexin B is legal.

United Kingdom. A web search found no statement from the UK medicines regulator naming orexin B, and its lists were not checked directly for this guide. UK sellers list orexin B as a research peptide and state that it is "not designed for human consumption or clinical application". [52]

Is Orexin B banned in sport? Does it show up on a drug test?

Orexin B is not named on the World Anti-Doping Agency's 2026 Prohibited List or its 2027 list, which takes effect on January 1, 2027. [48], [49] Category S0 bans at all times any substance with no current approval by any government health authority for human use, and the 2027 list adds "peptides" to its examples. [48], [49] Orexin B has no such approval anywhere, so athletes who are tested should treat it as prohibited. None of the sources reviewed describes a routine test that detects it.

Who should be especially cautious?

These groups have no safety data at all. That is a reason for caution, not proof of harm.

• Anyone with suspected narcolepsy or unexplained daytime sleepiness who has not seen a specialist. Diagnosis changes what is available, including an approved medicine. [40]
• Anyone with high blood pressure, heart disease or a heart rhythm disorder, given the blood-pressure and heart-rate rises seen with the approved OX2 receptor tablet. [40]
• Anyone with liver disease, given the liver injury that stopped an earlier OX2 receptor drug. [39]
• Anyone with bladder problems or an overactive bladder, given how common urinary frequency was with the approved tablet, whose label asks prescribers to screen for these symptoms. [40]
• Children and teenagers, and anyone pregnant or breastfeeding. Never studied; the approved OX2 receptor tablet is not established as safe or effective in children either. [40]
• Competitive athletes. See the anti-doping section above. [48]

Has Orexin B been tested alongside other medicines?

No. There is no interaction study of any kind. What can be said is indirect and worth raising with a pharmacist or doctor:

• The orexin blocker sleeping pills, such as suvorexant, act in the opposite direction, and suvorexant's label says it must not be used by people with narcolepsy. [51]
• The approved OX2 receptor tablet must not be combined with strong CYP3A inhibitors, a group of common medicines that slow its breakdown in the liver, and needs a lower dose with moderate ones. That shows this drug class can interact with everyday medicines, even though orexin B itself has never been tested. [40]
• Combining orexin B with stimulants or other wake-promoting medicines has never been studied, so any combination adds effects that no one has measured together.

Bring a complete list of everything you take to a pharmacist or doctor before adding anything.

What should be monitored while using Orexin B?

No regulator has written a monitoring plan for orexin B, and no study has measured anything after giving it to a person. [50] What follows is what the approved OX2 receptor tablet's label and the trials of that drug class tracked, clearly marked as coming from different molecules. It is background for a conversation with a clinician, not a personal testing plan.

Two things are worth raising with a clinician regardless. First, persistent daytime sleepiness deserves a proper diagnosis, because a sleep study or spinal-fluid test changes what treatment is possible. Second, Health Canada's advice for anyone who has used an unauthorized peptide and feels unwell is to talk to a healthcare professional right away, and it helps to say exactly what was taken. [46]

What do people in public communities report?

Almost nothing about orexin B on its own. Searches of 13 public Reddit communities on sleep, narcolepsy, nootropics and peptides returned 37 matching posts, many only loosely related, and four threads were worth including; none described someone using orexin B alone. [57], [58], [59], [60] A 2026 "peptide cheat sheet" post that lists an orexin B amount is a protocol list with seller referral links, not a report of use; it is covered with the website amounts. [64] Selected discussions are not a survey of users, and comment-only mentions could not be searched, so quieter reports may have been missed.

What the one positive report looks like

In a 2022 thread asking which orexin is more active, the original poster was planning a nasal spray and noted how little information exists on the two peptides' relative strength. One commenter who had used a blend described orexin B as "much more stimulation" and orexin A as "more of a sleep stabilizer". The same commenter said that other orexin products had made them dizzy and gave no amounts, in a thread that also discussed prescription wake-promoting drugs. [57] That is one impression from a blend product, and it cannot be credited to orexin B.

A 2025 thread asked whether orexin B could significantly reduce the need for sleep. It correctly described orexin B as the natural, moderately selective activator of the orexin 2 receptor, and no one replied with experience. [58]

Does "orexin B" in a post mean the peptide?

Often not. Public threads regularly mix up the two peptides (orexin A and orexin B) with the two receptors (OX1 and OX2). In a 2026 narcolepsy thread about orexin agonist drugs, one commenter described "Orexin B-receptors" as regulating sleep and wake, and another corrected them: there are orexin A and B peptides and orexin 1 and 2 receptors. [59] A 2025 insomnia post described seltorexant, an experimental sleep drug that blocks the orexin 2 receptor, as "an Orexin B antagonist". [60] When a post says "orexin B", check whether it means the peptide sold in vials, the receptor, or a drug that acts on the receptor.

How can you judge an orexin story?

Ask: was there a diagnosis, or is this someone tired for ordinary reasons? Which peptide, from which seller, and was it a blend? How much, by which route, and at what time of day? What else was running at the same time: prescribed stimulants, caffeine, a new sleep schedule? Was anything measured, or is it a morning impression? And given that injected orexin B did not reach the mouse brain intact, what route could plausibly explain the effect? [10]

In community education groups, teaching about orexin covers the system's biology and the approved medicines rather than the native peptides. Educators treat the new OX2 receptor tablet as something for diagnosed narcolepsy under a specialist, explain that the orexin-blocking sleep medicines work in the opposite direction, and warn that wake-promoting drugs hide sleep debt rather than remove the need for sleep. Member discussions in these groups never mention orexin B by name. When members asked about orexin peptides in general, the replies said no protocol was known and no one had seen the peptides for sale, so there are no member experiences, side effects or stopping reports to share for orexin B.

How does Orexin B compare with Orexin A and the orexin medicines?

Four different things get called "orexin" online. Two are the natural peptides, one is a new medicine that switches the orexin 2 receptor on, and one is a family of sleeping tablets that switch orexin receptors off.

Doserly

Orexin A and orexin B side by side

One gene, one parent protein (prepro-orexin), two different peptides. Cell and animal research.

Size and shape

Orexin A: 33 amino acids, two disulfide bridgesOrexin B (this guide): 28 amino acids, straight chain, no bridges

OX1 receptor binding

Orexin A: Strong (20 nM)Orexin B (this guide): About 20 times weaker (420 nM)

OX2 receptor binding

Orexin A: 38 nMOrexin B (this guide): 36 nM, about the same

Fat solubility

Orexin A: 0.232Orexin B (this guide): 0.030, about 8 times lower

From blood to brain (mice)

Orexin A: Crossed into the brain, mostly intactOrexin B (this guide): Broken down in blood; no intact peptide detected in the brain

Human dosing studies

Orexin A: Small single-dose studies (see its guide)Orexin B (this guide): None published

Orexin A has its own guide: Orexin A.

Orexin B is shorter, unbridged and prefers OX2, and in mice it was broken down in blood before reaching the brain.

Orexin A and orexin B are separate peptides, even though one gene makes both. They are cut from the same parent protein in the same nerve cells, but the finished molecules differ in three ways that matter. [1], [3] Orexin A is 33 amino acids long and pinned into shape by two disulfide bridges; orexin B is 28 amino acids long and has no bridges, so its shape is looser and less fixed. [3], [4], [6], [7] Orexin A activates both receptors about equally, while orexin B binds the OX1 receptor about 20 times more weakly in the original binding tests (5 to 100 times across later tests) and works mainly through OX2. [8], [9] And in a mouse study, orexin A injected into a vein crossed into the brain mostly intact, while orexin B was broken down in blood and no intact orexin B could be detected in the brain. [10] Later dog and imaging studies found orexin A's own entry into the brain from blood poor (see the Orexin A guide). In an "Orexin A/B" blend, there is no evidence the orexin B part reaches the brain. [10] The Orexin A guide covers its own human studies in detail.

The gap between the peptide and the medicine is the point. Oveporexton does what an orexin B product would be hoped to do: it switches on the OX2 receptor, and it reached approval after two phase 3 trials. [40] It is a small molecule taken by mouth with a half-life of about 23 hours, while orexin B is a peptide that, in mice, did not survive the bloodstream intact. [10], [40] Getting to an approved drug also took a failure: TAK-994, an earlier drug of the same kind, was stopped after liver injury. [39]

Common questions about Orexin B

Is Orexin B the same as hypocretin-2?

Yes. Two laboratories described the same peptide in 1998 and named it differently: orexin-B from one group and hypocretin-2 from the other. [1], [2] Both names appear in research papers and product listings, along with abbreviations such as OXB, OxB and Hcrt-2. Hypocretin-1 is the same molecule as orexin A, which is a different peptide from this one (see the comparison).

Is Orexin B the same as the orexin 2 receptor?

No. Orexin B is a peptide, a signal. The orexin 2 receptor (OX2R, also called HCRTR2) is the protein on nerve cells that receives the signal. [1], [3] Orexin B happens to prefer that receptor, which is why the two get mixed up, but orexin A binds it just as strongly. [8] The approved narcolepsy tablet is an orexin 2 receptor drug, and seltorexant, an experimental sleep drug, blocks the same receptor; neither is orexin B, and a post calling a receptor blocker an "Orexin B antagonist" is using the names loosely. [40], [60] See how it works.

Is Orexin B the same as Orexin A?

No. Both come from one parent protein, but orexin B is shorter (28 amino acids against 33), has no disulfide bridges, binds the OX1 receptor about 20 times more weakly in binding tests, and in mice was broken down in blood rather than crossing into the brain. [3], [8], [10] Orexin A has been given to people in a few small research studies, described in its own guide; orexin B never has. [50] Read the Orexin A guide or see the comparison.

Does Orexin B make you need less sleep?

No evidence says so, because it has never been tested in people. [50] The one public self-experiment plan that mentioned orexin B reserved pure orexin B for a top funding tier; the group later tested orexin A only and found no significant effect, and has published no orexin B result. [56], [70] In mice, an OX2-selective orexin B analogue put directly into the brain reduced narcolepsy signs, which is a different question from reducing sleep need in healthy people. [14] See what it is used for.

Is Orexin B a nasal spray or an injection?

Neither has been studied in people. [50] Sellers offer freeze-dried powder in 1 mg and 5 mg vials, and some sprays have been sold as orexin A and B blends. [52], [54], [56] Websites describe both routes: 100–200 mcg as a nasal spray when needed, or 50–250 mcg a day by injection, with no human study behind either. [62], [63], [64] There is no study of nasal orexin B in any species. In mice, orexin B injected into a vein was broken down in blood and did not reach the brain intact, and in sheep an intravenous dose had no effect on appetite. [10], [12] See how routes compare.

Is Orexin B the same as the new narcolepsy tablet?

No. Oveporexton, approved in the United States in August 2026 for adults with narcolepsy type 1, is a manufactured small molecule that switches on the orexin 2 receptor and is swallowed. Orexin B is a natural peptide. [40], [41] They share a target receptor, but only the tablet has been through large trials and has a label with doses, warnings and monitoring. [40] See the comparison.

Is it legal to buy Orexin B?

Nowhere is it an approved medicine. In the United States it is sold as research material and is not in the FDA substance database or on the FDA's compounding lists. [42], [44], [45] In Canada there is no authorized product, and Health Canada says unauthorized peptide products are illegal and unassessed. [43], [46] Australia's regulator says unapproved peptide products have not been evaluated for safety, quality or effectiveness. [47] A "research use only" label describes how a product is sold, not whether it is safe. See the dated legal summary.

Does Orexin B show up on a drug test?

Not on a standard drug test, and none of the sources reviewed describes a routine test for it. For athletes, that is not the same as being allowed. Orexin B is not named on the World Anti-Doping Agency's 2026 or 2027 lists, but category S0 bans any substance without approval from a government health authority, and the 2027 list names peptides as an example. [48], [49] See the sport rules.

Glossary

Plain explanations of the route, dosing and research terms used in this guide. Underlined terms in the text link here.

Adverse event

A harmful or unwanted medical event reported after someone used a treatment. A report alone does not prove the treatment caused it.

Agonist

A substance that switches a receptor on, copying the body's own signal. Orexin B is a natural agonist at the orexin receptors; oveporexton is a manufactured agonist at the OX2 receptor.

Amino acid

A small chemical building block. Chains of amino acids make up peptides and proteins. Orexin B is a chain of 28.

Animal study

Research in animals such as mice, rats, pigs or sheep. It shows what a substance does in a living body, but results in people can differ.

Antagonist

A substance that blocks a receptor so the body's own signal cannot act on it. The insomnia medicine suvorexant is an orexin receptor antagonist.

Blood-brain barrier

The tight lining of the brain's blood vessels, which keeps most large molecules in the blood from entering brain tissue. Orexin B did not get through it intact in mice.

Cataplexy

A sudden, brief loss of muscle strength triggered by strong emotion such as laughter, while the person stays awake. It is a defining feature of narcolepsy type 1.

Cell study (in vitro)

Research on cells or tissue grown in a dish. It gives early clues about biology, but it is far from proof of benefit in people.

Compounding

A pharmacy making a medicine for an individual patient from raw ingredients. In the United States, pharmacies may only compound with bulk ingredients on FDA's allowed lists; orexin B has not even been nominated.

Controlled trial

A study that compares people who receive a treatment with a similar group who do not, often receiving a placebo instead.

Creatine phosphokinase (CPK)

An enzyme that leaks from muscle into the blood when muscle is strained or damaged. The approved OX2 receptor tablet raised it in some patients.

Cerebrospinal fluid (CSF)

The clear fluid around the brain and spinal cord, sampled by a lumbar puncture. Its orexin A (hypocretin-1) level is used to diagnose narcolepsy type 1.

Disulfide bridge

A chemical link between two sulfur-containing amino acids that pins part of a peptide into a fixed shape. Orexin A has two; orexin B has none.

Half-life

The time it takes for the measured level of a substance in the blood to fall by half. It is not the same as how long an effect lasts. For orexin B, no measured value was found in the studies reviewed.

Hypothalamus

A small region deep in the brain that regulates sleep, appetite, body temperature and hormone release. Orexin-producing cells sit in its lateral and back parts.

Intramuscular (IM)

Injected into a muscle. One study gave orexin B this way, to young pigs.

Intranasal

Sprayed or dropped into the nose. No study has given orexin B this way in any species.

Intravenous (IV)

Given directly into a vein. In mice, no intact orexin B given this way could be detected in the brain; in sheep, it did not change eating.

Investigational

Still being studied and not approved by a regulator, such as the FDA, to treat any condition.

Freeze-dried (lyophilized)

Dried by freezing and removing the water, leaving a powder. Research peptide vials are sold this way and mixed with liquid before use.

Mass spectrometry

A laboratory method that identifies and counts molecules by their exact weight. It is more specific than the antibody-based kits often used to measure orexins in blood.

mcg and mg

Micrograms and milligrams. 1 mg equals 1,000 mcg. Orexin B vials are sold as 1 mg or 5 mg of powder.

Molar mass

The weight of one mole of a substance, in grams per mole. It converts a count of molecules (nanomoles) into a weight (micrograms). For orexin B it is about 2,899 g/mol.

Nanomole (nmol)

A way of counting molecules rather than weighing them. For orexin B, 1 nmol weighs about 2.9 micrograms.

Narcolepsy type 1

A long-term neurological condition with overwhelming daytime sleepiness and cataplexy, caused by the loss of most orexin-producing brain cells.

OX2 receptor (OX2R)

One of the two orexin receptors, also called HCRTR2 or the orexin 2 receptor. It is the one most tied to sleep and wakefulness, and the one orexin B prefers. It is a receptor, not a peptide.

Peptide

A short chain of amino acids. Peptides are usually broken down quickly in the body and do not survive being swallowed.

Pharmacokinetics

How the body absorbs, moves, breaks down and removes a substance. For orexin B, no human data exist.

Placebo

A dummy treatment with no active ingredient, used as a comparison in studies.

Preclinical research

Studies done before research in people: cell studies, tissue experiments and animal studies. All orexin B dosing research is preclinical.

Prepro-orexin

The parent protein that cells cut up to release orexin A and orexin B. One gene makes both peptides.

Receptor

A protein on a cell that recognizes a specific signal and changes the cell's behaviour when the signal arrives. Orexins act on two: OX1R and OX2R.

Research use only

A label on products sold for laboratory research. It does not mean a product is approved, tested for human use or legal to sell as a medicine.

Subcutaneous (SC)

Injected into the fatty layer just under the skin. No published study has given orexin B this way.

Syringe units

Markings on an insulin syringe that measure volume. On a U-100 syringe, 100 units equal 1 mL. The amount of peptide per unit depends on the vial's concentration.

WADA

The World Anti-Doping Agency, which publishes the list of substances banned in sport.

Explore more of the research

Go deeper into the experiments behind the claims.

Across this guide, the citations include 38 original research papers on orexin B and the orexin system: 5 studies measuring the body's own orexin B in people, 1 human trial of an OX2 receptor drug, and 32 animal, cell, tissue and chemistry studies (one of which also measured orexin B in patients' blood). Three reviews are cited separately. Paper counts are not counts of independent findings: several come from the same laboratories, and most were reviewed as abstracts.

How this guide was researched

This guide is built from a thorough review of the sources cited throughout it: published scientific studies, trial-registry searches, regulatory documents and the official label of a related medicine, product and protocol pages, and public forum discussions. We also reviewed community education groups where people discuss sleep, wakefulness and peptides.

The guide cites 70 sources, including 38 original research papers. Each type of source answers a different question. Studies show what researchers measured. Product and protocol pages show what is being sold and claimed. Personal accounts show what individual people experienced. Every numbered citation links to its entry below, labeled by source type.

How this guide was made

Research and drafting were AI-assisted. Every cited source was checked against the original, and the guide was reviewed and edited by Doserly before publication. It has not had an independent clinical review, and Doserly does not currently have medical reviewers. Doserly makes a medication and health-tracking app and runs Doserly Academy, both of which are promoted in this guide. Read our editorial policy for how guides are researched, updated and corrected.

This guide is for educational purposes. It summarizes what the reviewed sources report so the research is easier to understand; it is not medical advice. For a deeper dive, or to check any point for yourself, go straight to the cited sources.

Explore the sources