Skip to content
PeptideAI
Human trialsenergycognitionsleep

Orexin-A

The hypothalamic wakefulness neuropeptide whose loss causes narcolepsy, given intranasally in research settings to restore alertness and working memory after sleep deprivation.

Also known as hypocretin-1, OX-A, Hcrt-1

Human trials — Studied in people, typically early phase or small — promising rather than proven.

The orexin system itself is among the best-validated targets in sleep neuroscience, but the evidence for administering orexin-A intranasally is limited to small human studies in narcolepsy and to primate sleep-deprivation work. There is no large trial, no approved product, and formulation instability is a real obstacle. Pharmaceutical development has moved toward small-molecule orexin receptor agonists instead.

How it works

Orexin-A is produced by a small population of lateral hypothalamic neurons and projects broadly to the locus coeruleus, raphe, tuberomammillary nucleus and basal forebrain, where it stabilises the wake state. It binds both OX1R and OX2R with roughly equal affinity, unlike orexin-B. Selective loss of these neurons is the established cause of narcolepsy type 1, and orexin antagonists such as suvorexant are approved insomnia drugs, so this axis is unusually well validated. Intranasal delivery has been shown to reverse sleep-deprivation-induced cognitive deficits in monkeys and to affect sleep architecture and attention in narcolepsy patients. Its structure - the disulfide bridges and the amidated terminus - makes it fragile and hard to formulate, which is a large part of why nobody has turned it into a drug.

Targets: Orexin receptor 1 (OX1R), Orexin receptor 2 (OX2R), Locus coeruleus and ascending arousal system

Dosing

ProtocolDoseFrequencyRoute
Research intranasal protocolOn waking, or before a period of enforced wakefulness. Never in the second half of the day.400 mcg – 1 mgonce daily as neededintranasal
  • · Published human intranasal work in narcolepsy used roughly 435 mcg per administration. Grey-market protocols run 500-1000 mcg. Use it occasionally rather than daily - it is a tool for a bad night, not a substitute for sleeping.

Titration

Start at 250-400 mcg. Higher doses reliably raise heart rate and can produce a jittery, anxious quality.

Cycling

Intermittent use only. There is no data on chronic administration, and chronically overriding sleep pressure with an arousal peptide is a bad trade whatever the mechanism.

Work out your exact syringe units →

Pharmacology

Half-life
Short and not well characterised for the intranasal route; the peptide is rapidly degraded in plasma. Intranasal effects on alertness are reported over a few hours.
Onset
15-45 minutes intranasally; the effect is subjectively closest to being properly rested rather than stimulated.
Routes
intranasal
Molecule
33-amino-acid neuropeptide with a pyroglutamyl N-terminus, two intrachain disulfide bridges and a C-terminal amide
Sequence length
33 amino acids
Molecular weight
3562 Da

Handling

Diluent
Bacteriostatic water
Typical mix
1 or 2 mL
Vial sizes
5 mg
Lyophilised
Freezer for anything beyond a few weeks; fridge otherwise.
Reconstituted
Refrigerated and used within 14-21 days. Assume faster degradation than a simple linear peptide.
Light sensitive
Yes — keep it out of the light

Intranasal — usable, with a caveat

Intranasal orexin-A is one of the better-supported nose-to-brain cases: it has been shown to reach cerebrospinal fluid in primates and to reduce sleep-deprivation deficits in humans. The molecule is far too large and too short-lived to be useful any other way, so nasal is not a shortcut here, it is the only plausible route. It remains investigational everywhere.

Mixing

This peptide is fragile - two disulfide bridges mean it is genuinely sensitive to agitation, heat and pH. Reconstitute gently, do not shake, and do not expect a nasal bottle carried in a pocket to still be intact in a fortnight.

Side effects

  • commonIncreased heart rate— Orexin drives sympathetic outflow; this is mechanism, not contamination.
  • commonInsomnia if dosed late— The whole point of the molecule is to prevent sleep.
  • commonNasal irritation
  • uncommonRaised blood pressure
  • uncommonAnxiety or jitteriness
  • uncommonIncreased appetite— Orexin was named for its feeding effects before its arousal role was understood.

Do not use if

  • Uncontrolled hypertension or significant cardiac arrhythmia - it raises sympathetic tone.
  • Panic disorder - orexin signalling is directly implicated in panic and CO2-triggered anxiety.
  • Pregnancy and breastfeeding - no data.
  • Insomnia. Using a wake-promoting peptide to fix daytime fatigue caused by bad sleep makes the underlying problem worse.

Combining it

  • synergyneuropeptide-s — Both promote arousal through interacting hypothalamic systems; NPS acts partly via orexin neurons. Combining them stacks the same cardiovascular effects.
  • cautionsemax — Two activating compounds; the combination commonly produces overstimulation and poor sleep.

What to monitor

  • · Check resting heart rate and blood pressure before and about an hour after your first dose.
  • · Track total sleep time honestly - if it is dropping, stop.

Legal status

Not approved anywhere as a therapeutic. Sold as a research chemical; orexin receptor antagonists, by contrast, are approved insomnia drugs.

References

  • Deadwyler et al. 2007, systemic and nasal delivery of orexin-A reduces the effects of sleep deprivation on cognitive performance in nonhuman primates, Journal of Neuroscience (preclinical)
  • Weinhold et al. 2014, the effect of intranasal orexin-A on sleep, wakefulness and attention in narcolepsy with cataplexy, Behavioural Brain Research (trial)

Mechanism in depth

The orexin axis is one of the most thoroughly validated targets in all of sleep neuroscience, and it is worth separating that validation from the evidence for administering the peptide. Orexin-A is produced by a small population of lateral hypothalamic neurons projecting to the locus coeruleus, raphe, tuberomammillary nucleus and basal forebrain, where it stabilises the wake state rather than driving arousal in the way a stimulant does. Selective loss of those neurons is the established cause of narcolepsy type 1 - not a correlation, an established cause - and orexin receptor antagonists like suvorexant are approved insomnia drugs, so both directions of the axis have been validated in humans. Orexin-A binds OX1R and OX2R with roughly equal affinity, unlike orexin-B which prefers OX2R. What the human intranasal studies actually show is narrower and more specific than the popular account: in narcolepsy with cataplexy, 435 nmol of intranasal orexin-A reduced wake-to-REM transitions and REM sleep duration, increased N2 sleep in the subsequent night, and reduced false reactions on divided attention testing. The authors framed it as a REM sleep stabilising factor rather than a wake-promoting one. That is a real effect and it is not the same thing as a nootropic alertness drug. Two practical points follow. First, the dose in those studies was 435 nanomoles, which for a 3562 Da peptide is roughly 1.5 mg - considerably more than the sub-milligram figures usually quoted. Second, the structural fragility is a real obstacle rather than a footnote: pharmaceutical development moved toward small-molecule orexin receptor agonists precisely because this peptide is hard to formulate and hard to keep intact.

What usually goes wrong

The compound degrades in the vial and people blame themselves. Two disulfide bridges, a pyroglutamyl terminus and a C-terminal amide make this one of the genuinely fragile peptides in this class - it is sensitive to agitation, heat and pH in a way a simple linear heptapeptide is not, and a nasal bottle carried in a pocket for a fortnight is unlikely to still contain intact peptide. Aliquot and freeze. The second failure is chronic use: every property of this molecule argues for occasional deployment against a specific bad night, and daily use to override accumulated sleep pressure is a straightforwardly bad trade with no data behind it. Third, the dose confusion - the human trials used 435 nmol, roughly 1.5 mg, and much of the grey-market literature quotes 435 mcg as though the units were interchangeable. They are not, and someone dosing 435 mcg is at about a third of the studied amount. Fourth, cardiovascular naivety: this peptide raises heart rate and sympathetic tone by design, and people with undiagnosed hypertension or arrhythmia find that out the hard way. Fifth, the panic risk is specific and real rather than boilerplate.

Titration ladder

  1. 250 mcgFirst use — Single intranasal dose on waking, split between nostrils. Check heart rate and blood pressure an hour later. Higher doses reliably raise heart rate and can produce a jittery, anxious quality.
  2. 500 mcgSubsequent occasional use — The lower end of common grey-market protocols. Never in the second half of the day - the entire function of the molecule is to prevent sleep.
  3. 1 mgOccasional use, upper end — Top of grey-market protocols. Worth knowing that the published human narcolepsy studies used 435 nmol, which for a 3562 Da peptide is roughly 1.5 mg - so even this dose sits below the studied one. Intermittent use only; there is no data on chronic administration.

Bloodwork worth running

MarkerWhenWhy it matters
Resting heart rate and blood pressureBaseline before the first dose and approximately one hour after it, then before each subsequent use if you have any cardiac history.Orexin drives sympathetic outflow as part of its normal physiology. Increased heart rate on this peptide is mechanism, not contamination, and it is the effect most likely to matter in someone with undiagnosed cardiovascular disease.Act if: A rise of more than 15 bpm in resting heart rate, or more than 15 mmHg systolic, means the dose is too high or the compound is not for you. Uncontrolled hypertension or significant arrhythmia is a contraindication rather than something to monitor around.
Total sleep time, tracked objectivelyEvery night, with a wearable or a written log rather than recall, from before the first dose onward.This is the measurement that determines whether using orexin-A is a reasonable tool or an accelerating problem. A wake-promoting peptide taken to compensate for insufficient sleep quietly makes the underlying deficit worse while removing the signal that would have told you.Act if: Any downward trend in total sleep time across two weeks means stop. The compound is a tool for a bad night already had, not a way to have more of them.
A structured anxiety measure, if you are prone to panicBaseline, and after any use if you have a history of panic.Orexin signalling is directly implicated in panic and in carbon-dioxide-triggered anxiety. This is not a general caution - it is a specific and well-described role for this exact system, and panic disorder is a contraindication for good reason.Act if: Any panic symptoms means stop and do not retry.

Pharmacokinetics

Crosses blood-brain barrier
partial
Metabolism
Peptidase degradation. The molecule is structurally fragile - two intrachain disulfide bridges, a pyroglutamyl N-terminus and a C-terminal amide - and is as vulnerable to physical and chemical degradation in the vial as it is to enzymes in the body.
Elimination
Renal excretion of fragments and amino acids.

Receptor targets

  • Orexin receptor 1 (OX1R) — Orexin-A binds OX1R and OX2R with roughly equal affinity; orexin-B is OX2R-preferring. Specific Kd values I did not verify

    Gq-coupled signalling driving cortical activation and arousal, plus the sympathetic and appetite effects that come with it.

  • Orexin receptor 2 (OX2R) — Comparable to OX1R for orexin-A

    The receptor most closely tied to wake-state stabilisation. OX2R is the primary target of the approved orexin antagonist insomnia drugs, pointed in the opposite direction.

  • Locus coeruleus and the ascending arousal system — Downstream projection target rather than a receptor

    Stabilisation of the wake state and suppression of inappropriate REM intrusion. In the narcolepsy studies this showed as fewer direct wake-to-REM transitions rather than as a stimulant effect.

Trials

  • Intranasal orexin-A (hypocretin-1) on sleep, wakefulness and attention in narcolepsy with cataplexy Clinical trial, placebo-controlled crossover · n=14 · 2014

    Sleep architecture and attentional performance after 435 nmol intranasal orexin-A in narcolepsy with cataplexy. Fewer wake-to-REM transitions, decreased REM sleep duration, increased N2 sleep duration the following night, and fewer false reactions on divided attention testing. The authors characterised orexin-A as a REM sleep stabilising factor.

  • Effects of intranasal hypocretin-1 (orexin A) on sleep in narcolepsy with cataplexy (Baier et al. pilot) Clinical trial, pilot · n=8 · 2011

    Nocturnal sleep architecture after 435 nmol intranasal human recombinant hypocretin-1. No significant effect on nocturnal wakefulness, but reduced REM sleep quantity particularly in the second half of the night and significantly reduced direct wake-to-REM transitions. Established the feasibility of intranasal delivery of a therapeutic neuropeptide.

  • Olfactory dysfunction in narcolepsy with cataplexy restored by intranasal orexin-A Clinical trial · 2008

    Restoration of olfactory function in narcolepsy patients after intranasal orexin-A. An unusual and specific finding, published in Brain, and one of the clearer demonstrations that the intranasal route delivers biologically active peptide to central structures.

What to expect, and when

15-45 minutes intranasally, with the subjective quality closer to being properly rested than to being stimulated - which is a meaningful distinction and the main reason people like it. Effects on alertness are reported over a few hours. In the primate sleep-deprivation work the cognitive restoration was measured within the session. In the narcolepsy studies the interesting effects showed up in that night's and the following night's sleep architecture rather than as acute wakefulness, which suggests the molecule is doing something more like re-stabilising sleep-wake regulation than simply pushing arousal. There is no data on repeated or chronic administration at all.

Stacking and comparisons

Neuropeptide S is the combination to think hardest about: NPS acts partly through orexin neurons, so stacking them is not two independent arousal mechanisms but one system engaged twice, and the cardiovascular effects stack accordingly. Semax plus orexin-A is two activating compounds and reliably produces overstimulation and poor sleep. Caffeine is the realistic combination people actually make and it is the one worth being careful with - both raise heart rate and sympathetic tone, and the jittery quality at higher orexin doses is amplified considerably. The most important stacking note is a negative one: do not combine it with anything you are taking to compensate for chronic sleep debt, because that is a stack whose only function is to hide a deficit that is still accumulating. If you are reaching for orexin-A more than occasionally, the problem is the sleep, not the availability of the peptide.

Against modafinil, which is the honest comparison for the use case: modafinil has large human trials, regulatory approval, a known duration and a known adverse effect profile, and it costs almost nothing. Orexin-A has monkey data, small narcolepsy studies and a fragile expensive peptide that may or may not still be intact in your bottle. The theoretical appeal of orexin-A is that it works on the wake-stabilising system itself rather than downstream of it, and the primate work suggesting restoration of normal regional brain metabolism rather than override is genuinely interesting. That is a mechanistic argument, not an evidential one. Against caffeine: caffeine is adenosine blockade, which masks sleep pressure without addressing it; orexin engages the arousal system directly. Both cost you sleep if used late. Against Semax: Semax is stimulating through monoamines and neurotrophic over weeks; orexin-A is acute, specific and has nothing to offer for sustained cognitive work. Against actually sleeping, which is the intervention orexin-A is being used to avoid: sleeping wins, is free, and the compound's own contraindication list says so.

Rough cost

$60–$400/month. A 5 mg vial typically runs 80-200 USD, and this is one of the more expensive peptides in the class per milligram because it is difficult to synthesise correctly. At 500 mcg per use, occasional use of two or three times a week runs 60-150 USD monthly. Anyone attempting to reproduce the 435 nmol clinical dose of roughly 1.5 mg would get three doses per 5 mg vial. Given the fragility, assume some of every vial is lost to degradation.

Genuinely uncertain

  • No human pharmacokinetic data exists for intranasal orexin-A - no tmax, bioavailability, half-life, volume of distribution, clearance or protein binding.
  • The Core record states published human intranasal work used roughly 435 mcg per administration. The primary studies specify 435 nmol, which for a 3562 Da peptide is approximately 1.5 mg. This is a significant discrepancy and the nanomolar figure is what the papers report.
  • I did not verify specific Kd values for orexin-A at OX1R and OX2R and have not quoted any.
  • The full 33-residue sequence I did not verify against a primary source and have left the sequence fields blank rather than assert it.
  • Whether the primate sleep-deprivation findings translate to healthy sleep-deprived humans has never been tested.
  • There is no data on repeated or chronic administration in humans by any route.
  • How much intact peptide survives typical grey-market handling and storage is unknown, and given the disulfide bridges this is a substantial practical uncertainty about what people are actually taking.
  • The magnitude and duration of the cardiovascular effect at grey-market doses has not been characterised.
  • The molecular weight of 3562.0 Da is consistent with a 33-residue amidated peptide with two disulfides but I did not verify it against a primary characterisation.

Papers