Intranasal Peptides: What Works, What Absorbs, and What Can Irritate Your Nose?

Which peptides have actual nasal evidence?

The useful question is whether a peptide has been studied through the nose, in what formulation, and for which outcome. A compound can be absorbed without improving the condition being studied. It can also show promising effects after injection while its nasal delivery remains an open question.

This comparison includes human and animal research. The categories describe the evidence for the route, rather than ranking products for personal use.

Read the named research peptides, nasal-purpose development, absorption figures, irritation risks, or water-versus-saline comparison.

Semax and Selank: why the nasal route is part of their history

Semax and Selank have more than a seller’s decision to put powder in a spray bottle behind them. Their Russian manufacturer-hosted instructions describe finished nasal drops. That documents a product-development history; it does not make every similarly named research product equivalent. Semax leaflet; Selank leaflet.

For Semax, a 2006 rat experiment reported increased hippocampal BDNF protein, activation of its TrkB signalling system and improved performance in a conditioned-avoidance task after intranasal administration. This is useful positive animal evidence: researchers observed both a biological change and a behavioural result. Rat task performance does not establish improved memory, attention or stroke recovery in people. Dolotov and colleagues.

A 2018 human experiment enrolled 24 healthy volunteers: 14 received nasal Semax and 10 placebo. It reported an acute difference in a component of the brain’s default-mode network on resting-state fMRI. That supports a measurable brain-related response under the study conditions. It did not measure long-term cognitive benefit, and an fMRI change cannot quantify how much intact peptide reached the brain. Lebedeva and colleagues.

For Selank, a 2008 rat study compared intranasal, intravenous, intraperitoneal and intragastric administration of tritium-labelled peptides. The authors identified the nasal route as the most favourable of those tested for CNS delivery. This is directly relevant preclinical work, although tracking a label requires care when interpreting how much intact active peptide, rather than breakdown products, is present. The accessible abstract does not resolve that analytical detail. Ashmarin and colleagues.

The human evidence also deserves attention. A 2008 comparison involved 62 patients with generalized anxiety disorder or neurasthenia: 30 received Selank and 32 medazepam. The abstract reports similar anxiety effects, with additional effects attributed to Selank. An active-comparator report of this size is encouraging, but it does not establish equivalence to an established treatment; the accessible abstract supplies insufficient detail about blinding, route and other methods. Zozulya and colleagues.

The evidence above concerns the named peptides and specific preparations. It cannot automatically validate N-acetyl variants, amidated variants, mixtures of Semax and Selank, or a vendor’s different solvent and pump. Those changes need their own evidence.

PT-141: nasal activity is real, and so were the development problems

PT-141 can produce a biological effect after nasal administration. In a 2004 placebo-controlled study, blood exposure increased with the intranasal dose, and researchers measured erectile responses in healthy men and men with erectile dysfunction. Flushing and nausea were the most common adverse events. Diamond and colleagues.

The later record changes the interpretation of that early promise. Palatin’s 2009 annual filing reports that blood-pressure increases were a significant reason for discontinuing its nasal development as a first-line sexual-dysfunction treatment. The company proposed variable nasal uptake as a partial explanation for the blood-pressure effects, nausea and vomiting. That explanation is the developer’s hypothesis, rather than proof that variability was the only cause. Palatin’s development disclosure.

The current Vyleesi approval concerns subcutaneous bremelanotide for a defined form of low sexual desire in premenopausal women, not a nasal spray or treatment of male erectile dysfunction. Its label still warns about transient blood-pressure increases and contraindicates use with uncontrolled hypertension or known cardiovascular disease. Switching to an injection did not eliminate the molecule’s systemic risks. Vyleesi prescribing information.

For nasal PT-141, the central uncertainty is therefore product performance and benefit versus risk, rather than whether nasal activity is possible. The old trials do not supply a dependable injection-to-spray conversion for an unrelated product.

BPC-157: animal promise does not yet answer the nasal question

We did not identify a direct nasal BPC-157 absorption study in the reviewed sources. That is a bounded search finding, not proof that the route cannot work.

Two papers illustrate why route checking matters. In the 1997 rat rhinitis experiment, investigators administered BPC-157 intraperitoneally, into the abdominal cavity. They then put capsaicin in the nose to provoke inflammation. BPC-157 reduced some inflammatory findings, but it was never a test of BPC-157 nasal absorption. Kalogjera and colleagues.

The 2022 pharmacokinetic study used intravenous and intramuscular administration in rats and beagle dogs. Mean absolute bioavailability after intramuscular administration was approximately 14–19% in rats and 45–51% in dogs, depending on the tested condition. These are dose-normalized exposure comparisons with intravenous administration, not percentages of animals responding. Neither range measures nasal uptake, and the species difference itself cautions against translating an animal percentage straight into a human claim. He and colleagues.

The constructive next step would be a study measuring intact BPC-157 after a specified nasal formulation, followed by local tolerability and outcome testing. Evidence for effects elsewhere in an animal cannot fill those gaps. Our bone and joint peptide review covers the broader biological rationale separately.

DSIP: a nasal human report exists, but it is not a sleep-treatment trial

It would be inaccurate to say DSIP has never been studied intranasally in humans. A 2001 publication is explicitly titled Intranasal administration of delta sleep-inducing peptide increases P300. PubMed indexes it as a letter/comment with human, double-blind and crossover-study terms. No abstract is available in that record; we could verify the publication, but not inspect its full methods and results. Hruz and colleagues.

P300 is an event-related electrical brain response associated with stimulus processing. A reported P300 change does not establish more deep sleep, improved insomnia or a known fraction of peptide absorbed. This paper therefore belongs in the nasal evidence map with a clear access and endpoint limitation.

The better-known 1992 insomnia study involved 16 patients and intravenous DSIP, with weak findings that the investigators did not consider likely to provide major short-term therapeutic benefit. It should neither be relabelled as a nasal trial nor ignored when discussing the sleep claim. Bes and colleagues. Our DSIP evidence review discusses the wider sleep literature.

Are any peptides designed specifically for the nose?

Yes, there are deliberately developed nasal peptide products. “A molecule can only work through the nose” is a much stronger claim.

Nafarelin’s Synarel formulation is an established example of a nasal peptide medicine. Semax and Selank have nasal-drop development histories. Davunetide, also called NAP, is an experimental example of a neuroprotective peptide taken into clinical development with intranasal delivery. These cases answer the product-design question without implying that another route is chemically impossible. Synarel; Semax; Selank; davunetide trial.

Davunetide also shows why delivery and efficacy must be evaluated separately. Its 2014 trial randomized 313 people with progressive supranuclear palsy, 157 to davunetide and 156 to placebo, and found no benefit on the primary clinical outcomes after 52 weeks. That result applies to the population and regimen studied; it does not show that all nasal peptides fail. Original trial.

The reason for continued optimism is experimental evidence of delivery itself. In a 2020 rhesus-macaque study, investigators used deuterium-labelled oxytocin and mass spectrometry to distinguish administered oxytocin from the animal’s own hormone. They detected labelled oxytocin in selected brain regions after nasal administration, but not after intravenous administration under the conditions tested. That is stronger evidence than an unverified subjective effect or a generic “crosses the blood–brain barrier” claim. It remains an animal finding for oxytocin and the studied delivery conditions. Lee and colleagues.

How much absorption is lost?

There is no defensible single “nasal absorption loss” percentage for peptides. First specify what is being measured:

• Systemic bioavailability: how much dose-normalized exposure to intact drug reaches the circulation, usually compared with intravenous administration.
• Brain exposure: how much reaches a brain region or cerebrospinal fluid. A blood measurement cannot simply substitute for this.
• Clinical effect: whether the person benefits. A potent drug can work at low systemic exposure; measurable exposure can also produce no useful benefit.

The available numbers make the range of possibilities more concrete.

For calcitonin, the cited range corresponds to approximately 95–97% lower dose-normalized systemic exposure than the intramuscular comparator. That is arithmetic about exposure, not proof that the remainder was all swallowed or destroyed, and not an instruction to compensate with a larger dose.

The high Semax/Selank figures deserve the same scrutiny as low ones. FDA’s 2026 Semax assessment reports that it could not locate human pharmacokinetic studies for Semax free base or acetate by any route. A percentage repeated in product literature should consequently remain attributed to that literature rather than presented as independently verified human absorption. FDA assessment, page 39.

Some material may remain in the device, leave the nose, move toward the throat with mucus, break down, or cross the nasal lining. The balance depends on the drug and finished product. A taste in the throat or a rapid subjective sensation does not measure that balance. Nasal disease adds variability: the desmopressin label specifically warns that scarring, swelling and other mucosal abnormalities can make absorption unreliable. Desmopressin label.

Does “nose to brain” bypass all these problems?

No. Nose-to-brain transport is a legitimate research pathway, but it is not a guarantee attached to the word intranasal. Human work with insulin, vasopressin and an ACTH-related fragment reported increased cerebrospinal-fluid exposure after nasal administration; the macaque oxytocin study measured selected brain regions directly. Neither proves an equivalent delivered fraction for BPC-157, DSIP or a different spray device. Born and colleagues; oxytocin experiment.

Clinical outcomes still need testing. A 2020 intranasal-insulin trial randomized 289 participants; its primary analysis used 240 participants receiving the second delivery device, after reliability problems with the first device. It found no cognitive or functional benefit in that primary cohort over 12 months. A 2021 trial of intranasal oxytocin randomized 290 children and adolescents with autism and found no significant advantage in social or cognitive outcomes over 24 weeks. These are limits on specific treatment claims, not a dismissal of the route. Insulin trial; oxytocin trial.

Why can a peptide spray burn?

Burning is a tolerability symptom, not evidence of absorption or potency. Several parts of a formulation can matter: its acidity, dissolved-solute concentration, preservative system, active ingredient, and contact with an already inflamed or damaged lining. FDA’s nasal-product guidance treats pH, relevant osmolality specifications, microbial quality and delivered-dose performance as properties to characterize in the finished product. Nasal-product guidance.

This is not merely a theoretical concern. Semax’s manufacturer-hosted leaflet lists mild nasal-mucosal irritation with prolonged use. Calcitonin nasal prescribing information describes rhinitis, nosebleeds and nasal ulceration, and instructs clinicians to assess nasal complaints. Those examples show why discomfort should be investigated; they do not estimate the risk from another peptide. Semax leaflet; calcitonin label.

Persistent burning, recurrent bleeding, sores or a change in smell warrant stopping the suspect product and seeking clinical assessment, rather than trying to overcome the symptoms with more sprays. Breathing difficulty or swelling of the lips, tongue or throat requires urgent medical help.

There are also risks that a comfortable nose cannot detect:

• Systemic effects: blood-pressure changes and nausea are relevant to bremelanotide; severe hyponatremia is a known desmopressin risk. Nasal administration does not confine a drug to the nose. Vyleesi; Stimate.
• Microbial contamination: a reused bottle, ingredients and handling can introduce contamination. A preservative requires evidence of effectiveness in the finished formulation, rather than an assumption based on its presence. FDA guidance.
• Degradation, impurities and immune reactions: peptide identity and concentration can change during storage or formulation. FDA’s Semax assessment identifies aggregation and peptide-related impurities as immunogenicity concerns; it does not provide a reliable rate of these events in users. FDA assessment.

Bacteriostatic water or saline?

Bacteriostatic water for injection is not a validated default nasal diluent. Saline is familiar in nasal products, but adding a peptide changes the formulation and requires its own compatibility and stability evidence. Neither label on a diluent settles the safety of the final spray.

The two 0.9% figures refer to different chemicals: benzyl alcohol in common bacteriostatic water versus sodium chloride in normal saline. They are not interchangeable ingredients. Benzyl alcohol is also different from benzalkonium chloride, a preservative found in some nasal medicines; evidence about one should not be casually attributed to the other. Bacteriostatic-water label; Stimate ingredients.

Plain water, saline and a preservative each address different formulation questions. Preservatives inhibit microbial growth under appropriate conditions; they do not sterilize contaminated powder. Likewise, dissolving a peptide successfully does not show that it remains intact or that every spray delivers a consistent amount. The preparation needs a validated composition and storage period from its manufacturer or a qualified pharmacist, rather than a borrowed injectable recipe. FDA formulation guidance.

What evidence should accompany a credible nasal-peptide claim?

The comparison above suggests four useful questions for evaluating a claim:

1. Was this exact peptide administered intranasally? Record the species and distinguish the parent peptide from modified analogues or blends.
2. What was measured? Intact drug in blood, drug in brain tissue, an imaging signal and symptom improvement answer different questions.
3. Was the finished product characterized? Look for nasal tolerability, stability, microbial control and consistency of delivery from the actual container.
4. Does the conclusion match the experiment? A positive animal result can support further development without establishing a treatment effect in humans.

A certificate showing identity, purity or vial content can help answer a narrower quality question. It does not by itself establish nasal absorption, absence of microbes, stability after dilution or clinical benefit. Our guide to verifying a peptide COA explains how to check what a laboratory report actually tested.

Method, limitations and corrections

Evidence reviewed September 27, 2026. TitrateLab Research Desk prepared this AI-assisted, targeted literature synthesis around nasal-route evidence for Semax, Selank, BPC-157, DSIP and PT-141, with established nasal medicines and other development programs as comparators. We searched PubMed/Europe PMC and primary publisher records, product labelling, FDA materials and the developer’s historical filings. Search terms paired compound names and synonyms with intranasal, nasal, bioavailability, pharmacokinetics, irritation and related terms. Positive, negative, human and animal findings were eligible.

This is not a systematic review or a pooled efficacy analysis. No vendor spray was tested. The comparison is selective, and an unsuccessful search does not prove a study does not exist. Some older papers were assessable only through their indexed abstracts; the DSIP nasal report was assessable only through its title and indexing. Manufacturer leaflets establish what the manufacturer reports, with their numerical claims distinguished from inspectable primary study results. Product labels cited here do not establish current stock availability or approval in every country.

This article provides research context, not individualized treatment, dosing or compounding instructions. For our evidence practices, see TitrateLab’s methodology. Send corrections with the article URL and supporting primary source to [email protected].