Nasal Spray or Injection: What the Route Evidence Shows for PT-141 and Melanotan-2
How the human evidence differs for nasal and injected PT-141 and Melanotan-2, and where that evidence runs out.
Research use only. PT-141 (bremelanotide) and Melanotan-2 are sold here as laboratory research materials, not for administration to a person or animal. Doses below describe only what published studies administered: nothing here is a dose, a spray volume, a reconstitution ratio, a device recommendation, or an administration instruction.
TL;DR: what the route evidence actually shows
PT-141 has real human data on both routes. Two intranasal studies and a subcutaneous clinical programme exist for bremelanotide. Melanotan-2 has none. Every published human study used subcutaneous dosing; none has given it intranasally or compared the routes. The nasal-versus-injection nausea question has never been measured. No study compares nausea or adverse-event rates head to head between routes. PT-141 became an injection for a documented reason, not the forum story. The 2007 filings do not use the term clinical hold; what they document is an FDA concern about efficacy and clinical benefit, plus blood-pressure increases. Nasal peptide delivery normally costs most of the dose. Nasal bioavailability for peptides is normally under 1 percent; the approved nasal peptides that beat that do it with potency and formulation, and still remain in the single digits.
Cyclic heptapeptide (bremelanotide) that acts as a melanocortin receptor agonist at MC3R and MC4R in the central nervous system. The active metabolite of Melanotan-II, studied for sexual-function endpoints via a central rather than vascular pathway.
Tanning peptide that activates melanin production in the skin. Stimulates melanocyte receptors for natural UV-free pigmentation. Also researched for appetite regulation and libido effects.
USP-grade sterile water with 0.9% benzyl alcohol (near-neutral, pH 6.2 to 6.4) - the standard solvent for reconstituting lyophilized peptides. Essential accessory for any peptide research. Each vial is sealed and ready to use.
Growth hormone secretagogues and gonadotropins
The question people actually ask
It arrives in two parts: does a nasal version of PT-141 or Melanotan-2 work, and is it easier on the stomach? It is one of the most repeated route questions on peptide-research forums.
This article covers what the published record supports, not how to prepare or dose a nasal spray, spray volume, switching routes, device choice, or whether nasal products sold online contain what their labels claim: administration questions for material not sold for human use.
PT-141 was studied by both routes
Bremelanotide (PT-141) was studied intranasally before it was studied as an injection. The intranasal phase 1/2 programme (Diamond LE et al., Int J Impot Res 2004;16(1):51-9, PMID 14963471) enrolled healthy men and men with mild-to-moderate erectile dysfunction: median time to peak plasma concentration 0.50 hours, mean half-life 1.85 to 2.09 hours, first erection around 30 minutes, and a statistically significant response above 7 mg nasal doses, with no maximum tolerated dose identified. Flushing and nausea were the most common adverse events, unquantified, a gap that matters later; the same abstract reports no clinically significant changes in vital signs, labs, ECGs or physical exams in that study.
A second intranasal study combined PT-141 with a PDE5 inhibitor (Diamond LE et al., Urology 2005;65(4):755-9, PMID 15833522): 19 men, crossover, PT-141 7.5 mg plus sildenafil 25 mg, both subtherapeutic doses, so it says nothing about higher-dose nasal PT-141 alone.
An early subcutaneous dose-ranging study in healthy men tested 0.3 to 10 mg and found a significant response above roughly 1.0 mg (PMID 14999221). Line up the thresholds, above 7 mg nasal versus above 1.0 mg subcutaneous, and it looks like a potency gap, but the numbers come from two separate studies with different endpoints, populations and stimulation conditions: an indirect, cross-trial comparison, not a controlled ratio.
The approved product, Vyleesi, is a subcutaneous autoinjector, not a nasal spray. Its phase 3 numbers are in our dedicated PT-141 evidence article rather than repeated here. There is no EU marketing authorisation for bremelanotide; approval is US only.
Why it became an injection, and why the usual story is wrong
A popular forum claim says the FDA shut down intranasal bremelanotide outright by regulatory order, but the phrase 'clinical hold' does not appear once in Palatin Technologies' Form 10-K for the fiscal year ended 30 June 2007.
What is documented is quotable: a joint Palatin/King Pharmaceuticals press release, filed 30 August 2007 as Exhibit 99 to a Form 8-K (SEC accession 0001088020-07-000039), states: "After reviewing the data generated in the Phase 1 and 2 studies, the FDA questioned the overall efficacy results and the clinical benefit of this product in both the general and diabetic ED populations, and cited blood pressure increases as its greatest safety concern." The release adds the FDA was open to a different pathway, for example second-line therapy for PDE5 non-responders, a company release quoting a regulatory conversation, not a published FDA letter.
Palatin's FY2007 10-K describes delaying phase 3 initiation for erectile dysfunction after FDA responses in late August 2007 raised serious concerns about benefit-to-risk. King Pharmaceuticals terminated the co-development agreement in early December 2007; the two companies' own filings differ by a day on the effective date, so the exact day is not worth stating.
Palatin's FY2008 10-K states bremelanotide had been studied across nasal, subcutaneous and intravenous formulations, almost 2,000 patients receiving at least one dose and about 1,500 receiving multiple doses, with blood-pressure increases a significant factor in discontinuing it as a first-line therapy. Those exposure figures cover the whole programme, never the nasal spray alone.
The company was more specific elsewhere, and this is the part the forum version leaves out. Announcing the subcutaneous trial, Palatin wrote that "increases in blood pressure observed in some patients receiving nasally administered bremelanotide, coupled with significant variation in plasma levels, lead to discontinuation of nasally administered bremelanotide as a first-line therapy for sexual dysfunction", and described the new study as designed to test "our hypothesis that increases in blood pressure and gastrointestinal events seen with intranasally administered bremelanotide were primarily related to high intranasal absorption in a subset of patients". So the sponsor did attribute the signal to the nasal route, and offered variable nasal absorption as the explanation. Two things to hold onto: this is the developer's own attribution and its own hypothesis, not an independent finding, and no trial ever compared the two routes head to head to test it.
What supported the switch (FY2009, FY2010 10-Ks): a phase 1 study of 45 repeat subcutaneous doses over two weeks found no statistically significant difference in mean blood-pressure changes versus placebo, and separately reported significantly decreased variability in plasma exposure under subcutaneous dosing; a follow-up safety study dosed 49 healthy men aged 45 to 65, 19 of them in a graded treadmill sub-study. Keep the two findings apart: the blood-pressure comparison was against placebo, while the exposure-variability observation describes the subcutaneous route itself. Neither was a head-to-head test against the nasal route, so neither establishes superiority or a tolerability advantage.
Melanotan-2: no route data at all
Melanotan-2 has never been evaluated by any route other than subcutaneous injection in any published human study we could locate. The founding pilot (Dorr RT et al., Life Sci 1996;58(20):1777-84, PMID 8637402) enrolled 3 male volunteers, subcutaneously. Larger studies extend that record, covered in our Melanotan-1 vs Melanotan-2 comparison rather than repeated here.
No published human study has given melanotan-2 intranasally or compared a nasal and subcutaneous dose. That absence is checkable: a ClinicalTrials.gov search for the term melanotan, run 26 August 2026, returns exactly one registered study, and it is not a nasal-route trial.
The only documented human exposure to a nasal melanotan-2 product in the literature is one case report (PMID 40210573): a 22-year-old woman self-administered an unlicensed melanotan-2 nasal spray for tanning and was diagnosed with biopsy-confirmed mucosal malignant melanoma of the anterior maxilla, treated by surgical resection, a temporal association, not causation, to be neither softened away nor inflated into a general warning.
A case report is not a rate
One published case means something happened once, in one person: no denominator, no comparison group, no way to rule out other factors, and no percentage or general outcome to draw from it. It belongs in the record because it is documented and specific, and no rate can be read from it.
The UK's MHRA confirmed, via an FOI response (FOI 21/1237, 20 December 2021), that nasal melanotan-II sprays circulate alongside injectables, are not automatically regulated as medicines, and that it had received 13 suspected adverse-drug-reaction reports for melanotan-II between 1 January 2011 and 9 December 2021. Sweden's Läkemedelsverket states all sale is illegal there, sold as both injectable powder and nasal spray, and advises against all use; the page makes no EU-wide approval statement. Fuller detail: our safety article.
A different molecule, often confused with it: afamelanotide, brand name SCENESSE, a linear 13-residue alpha-MSH analogue given as a 16 mg subcutaneous implant, EMA marketing authorisation issued 22 December 2014 for phototoxicity prevention in erythropoietic protoporphyria, authorised under exceptional circumstances. Melanotan-2 is a structurally distinct cyclic lactam-bridged heptapeptide, with no marketing authorisation in the jurisdictions cited here and no nasal-route human data.
Why the nose is a hard route for peptides
Nasal bioavailability of peptide and protein drugs is normally below 1 percent (Ozsoy Y et al., Molecules 2009;14(9):3754-79, PMID 19783956). Part of the reason is size: permeability across human nasal epithelial cell monolayers runs inversely with molecular weight, and insulin crossed roughly an order of magnitude slower than two smaller peptides in an in-vitro model (Kissel T, Werner U, J Control Release 1998;53(1-3):195-203, PMID 9741927). Both PT-141 and melanotan-2 are cyclic heptapeptide alpha-MSH analogues, smaller than insulin but still subject to that barrier. The other part is mechanical: mucociliary clearance moves mucus toward the pharynx at roughly 8 to 10 mm per hour (Gizurarson S, Biol Pharm Bull 2015;38(4):497-506, PMID 25739664), carrying drug away.
Approved nasal peptide products show the cost:
- Species
- Human, n=15
- Measured
- Mean systemic bioavailability, nasal
- Result
- 2.82%
- Species
- Human, n=12
- Measured
- Bioavailability vs subcutaneous injection
- Result
- roughly 8%
- Species
- Rat
- Measured
- Absolute bioavailability
- Result
- 7.7%
- Species
- Rat
- Measured
- Absolute bioavailability
- Result
- 26.8%
- Species
- Rat
- Measured
- Absolute bioavailability
- Result
- 1.22%
Nafarelin's figure comes from 15 healthy volunteers (Chaplin MD, Am J Obstet Gynecol 1992;166(2):762-5, PMID 1531580); the desmopressin figure from Andersson KE et al., Pharm Res 2019. Both remain far below injection levels.
The calcitonin rows are rat data, read as such: the same drug, same spray category, ranged from 1.22% to 26.8% across two studies and a formulation change, the lesson being that a nasal spray is not one fixed thing. Formulation, not the drug alone, decides how much of a nasal dose reaches circulation, and no equivalent optimisation work has been published for PT-141 or melanotan-2 given nasally.
Does the route change the nausea?
MC4R is expressed in the dorsal motor nucleus of the vagus, the same hindbrain dorsal vagal complex region as the area postrema, shown in transgenic reporter mice (Liu H et al., J Neurosci 2003). That is receptor localisation in an animal model, not a demonstrated human nausea mechanism, and localisation alone predicts nothing about how a route will be tolerated. It is why melanocortin nausea is usually discussed as a brainstem effect rather than a local reaction at the site.
The numbers that exist come almost entirely from the subcutaneous side: in the bremelanotide phase 3 integrated safety analysis, 1247 participants, nausea occurred in 40.0% versus 1.3% on placebo and was the leading reason for discontinuation (PMID 35147466); our PT-141 evidence article carries this table in full. The intranasal side has a signal but no number: the 2004 study reported nausea and flushing as the most common adverse events without quantification (PMID 14963471). That is the crux: one route has a documented rate, the other a documented signal with no number, and they cannot be compared in magnitude.
Broader class context, from a different agonist: pooled nausea across 7 setmelanotide trials, n=185, was 36% (PMID 39924461). Setmelanotide is subcutaneous-only, so this is single-route class context, not a route comparison.
No published study, for any melanocortin agonist, compares nausea or adverse-event rates head to head between routes. The honest answer to whether the spray causes less nausea: nobody has measured it, and the mechanism gives no reason to expect the route alone to remove a centrally mediated effect.
What we do not answer here
- How to prepare or dose a nasal spray. An administration instruction for material not sold for human use.
- Spray volumes or concentrations. Not published for either compound.
- Whether to switch routes. No trial has compared them.
- Which device to use. Outside this listing's scope.
- Whether any nasal product sold online contains what its label claims. UK Trading Standards testing has found inconsistent content; we cannot verify others' labels.
What you can check instead
Identity and purity have nothing to do with which route a compound was studied by. Each lot's batch certificate is at /coa, testing methodology at /purity: a literature question, not a release-testing one, so a correctly identified, correctly quantified vial can still have zero nasal-route human data behind it.
Match the lot to the vial
The certificate must carry the same lot or batch code printed on the vial.
Read identity and content, not route claims
A CoA confirms the molecule by mass and reports measured purity, nothing about which route has human data.
Read the water separately
Diluent documentation (sterility, pH, endotoxin) is its own certificate, unrelated to which route a peptide is discussed for.
Do not treat a route claim as evidence
Nasal-ready or fast-acting is marketing, not a citation. Published data is checkable by PMID, as here.
Where PT-141 and Melanotan-2 sit next to what else we list
The product-level detail for each compound sits in PT-141, research buying guide and Melanotan-2, research buying guide.
Melanocortin peptides we list
Cyclic heptapeptide (bremelanotide) that acts as a melanocortin receptor agonist at MC3R and MC4R in the central nervous system. The active metabolite of Melanotan-II, studied for sexual-function endpoints via a central rather than vascular pathway.
Tanning peptide that activates melanin production in the skin. Stimulates melanocyte receptors for natural UV-free pigmentation. Also researched for appetite regulation and libido effects.
Diluent and storage
USP-grade sterile water with 0.9% benzyl alcohol (near-neutral, pH 6.2 to 6.4) - the standard solvent for reconstituting lyophilized peptides. Essential accessory for any peptide research. Each vial is sealed and ready to use.
Transparent storage box with 10 individual compartments for 1-3 ml peptide vials. Stackable, fridge-friendly, travel-safe. Ideal for organising bacteriostatic water, GLP-1, BPC-157, and similar vials.
Frequently asked questions
Sources
- Diamond LE, Earle DC, et al. Intranasal bremelanotide, phase 1/2. Int J Impot Res. 2004;16(1):51-9. PMID 14963471. https://pubmed.ncbi.nlm.nih.gov/14963471/
- Diamond LE, Earle DC, et al. Intranasal bremelanotide with sildenafil, crossover. Urology. 2005;65(4):755-9. PMID 15833522. https://pubmed.ncbi.nlm.nih.gov/15833522/
- Rosen RC, Diamond LE, Earle DC, et al. Evaluation of the safety, pharmacokinetics and pharmacodynamic effects of subcutaneously administered PT-141, a melanocortin receptor agonist, in healthy male subjects and in patients with an inadequate response to Viagra. Int J Impot Res. 2004;16(2):135-42. PMID 14999221. https://pubmed.ncbi.nlm.nih.gov/14999221/
- Palatin Technologies, Inc. Form 10-K filings, FY2007-FY2010 (years ended 30 June). SEC.
- Palatin Technologies / King Pharmaceuticals joint press release, 30 August 2007, Exhibit 99 to Form 8-K. SEC accession 0001088020-07-000039.
- Dorr RT, Lines R, Levine N, et al. Life Sci. 1996;58(20):1777-84. PMID 8637402. https://pubmed.ncbi.nlm.nih.gov/8637402/
- ClinicalTrials.gov, search: melanotan. https://clinicaltrials.gov/search?term=melanotan
- Yassin Alsabbagh A, Bhujel N, Singh RP. Melanotan II nasal spray: a possible risk factor for oral mucosal malignant melanoma? Int J Oral Maxillofac Surg. 2025;54(9):806-808. PMID 40210573. https://pubmed.ncbi.nlm.nih.gov/40210573/
- Medicines and Healthcare products Regulatory Agency. Freedom of Information response 21/1237, 20 December 2021 (melanotan II: regulatory status and Yellow Card reports).
- Lakemedelsverket (Swedish Medical Products Agency). Melanotan 2, consumer information page. https://www.lakemedelsverket.se/
- Ozsoy Y, Gungor S, Cevher E. Molecules. 2009;14(9):3754-79. PMID 19783956. https://pubmed.ncbi.nlm.nih.gov/19783956/
- Kissel T, Werner U. J Control Release. 1998;53(1-3):195-203. PMID 9741927. https://pubmed.ncbi.nlm.nih.gov/9741927/
- Gizurarson S. Biol Pharm Bull. 2015;38(4):497-506. PMID 25739664. https://pubmed.ncbi.nlm.nih.gov/25739664/
- Chaplin MD. Am J Obstet Gynecol. 1992;166(2):762-5. PMID 1531580. https://pubmed.ncbi.nlm.nih.gov/1531580/
- Andersson KE, Longstreth J, Brucker BM, et al. Pharmacokinetic and Pharmacodynamic Properties of a Micro-Dose Nasal Spray Formulation of Desmopressin (AV002) in Healthy Water-Loaded Subjects. Pharm Res. 2019;36(6):92. PMID 31037429. https://pubmed.ncbi.nlm.nih.gov/31037429/
- Sridharan K, Sivaramakrishnan G. Adverse event profile of setmelanotide in obesity: an integrated assessment and systematic review using disproportionality analysis. Expert Opin Drug Saf. 2026;25(8):1507-1516. PMID 39924461. https://pubmed.ncbi.nlm.nih.gov/39924461/
- Liu H, Kishi T, Roseberry AG, et al. Transgenic mice expressing green fluorescent protein under the control of the melanocortin-4 receptor promoter. J Neurosci. 2003;23(18):7143-54. PMID 12904474. https://pubmed.ncbi.nlm.nih.gov/12904474/
- Clayton AH, Kingsberg SA, Portman D, et al. Safety Profile of Bremelanotide Across the Clinical Development Program. J Womens Health (Larchmt). 2022;31(2):171-182. PMID 35147466. https://pubmed.ncbi.nlm.nih.gov/35147466/
- Palatin Technologies, Inc. Announces Dosing of Subcutaneous Bremelanotide Trial in Men. Company press release. https://palatin.com/press_releases/palatin-technologies-inc-announces-dosing-of-subcutaneous-bremelanotide-trial-in-men/
- Sinswat P, Tengamnuay P. Enhancing effect of chitosan on nasal absorption of salmon calcitonin in rats. Int J Pharm. 2003;257(1-2):15-22. PMID 12711157. https://pubmed.ncbi.nlm.nih.gov/12711157/
Research use only. PT-141 (bremelanotide) and Melanotan-2 are supplied for laboratory research, not for human or animal administration, not as cosmetics, and not as medicines. Nothing in this article is a dosing, injection, nasal-administration, or medical instruction.
Research context for English-speaking buyers
Most of our English-speaking customers ship to the UK, Ireland, Malta or other English-as-second-language EU territories. The regulatory picture differs per country.
- Relevant authorities
- MHRA (UK, post-Brexit), HPRA (Ireland, EU-aligned), FDA Section 503A bulks list (US, restricted Cat 2 status of several peptides as of 2026)
- Customs and VAT
- EU shipments include 19% VAT; UK shipments after Brexit are now extra-EU and may attract UK VAT plus a handling fee at import
- Typical shipping window
- EU 2-4 working days, UK 4-7 working days, other international 7-14 working days, depending on customs
Research-grade peptides shipped from our EU warehouse are sold for laboratory use only and are not authorised for human or veterinary therapeutic application in any of the destination jurisdictions. US customers should be aware that the FDA Section 503A bulks list classification (and the April 2026 reclassification of twelve compounds) only governs compounding pharmacies, not direct-to-researcher imports for non-clinical work. UK buyers should declare the consignment on import and may be asked for a research justification by HMRC. We provide a CoA per batch identified by colour code rather than serial number; customs sometimes asks for this document when clearing the parcel.