Peptide forms compared: vials, pills, sprays and more

• Lyophilized vials are the default form: BPC-157 vials are priced at 93 vendors. Human studies comparing subcutaneous with intramuscular injection exist only for hormones such as hCG, and no in-use stability study of a reconstituted research-peptide vial was found.
• Pre-mixed liquids and pens: the studies are quality tests of compounded and counterfeit GLP-1 products. No stability study of a pre-mixed research-peptide vial was found.
• Capsules and tablets: approved oral semaglutide shows a swallowed peptide can reach the blood with an absorption enhancer, at a modelled 0.8% of the dose. Oral BPC-157 and KPV have animal studies only.
• Sublingual forms and strips: three small human studies, of oxytocin, desmopressin and GLP-1, none of a research peptide. No study of a peptide strip was found.
• Nasal sprays have the strongest form evidence for a research peptide: randomized trials of intranasal PT-141. Semax has one open-label study; BPC-157, GHK-Cu and NAD+ sprays have none.
• Topicals: GHK-Cu skin trials are small and cosmetic, and skin penetration of GHK-Cu or BPC-157 has not been measured.
• Bioregulators: no study has measured one of these short peptides in the blood after it was swallowed, and the human reports come mostly from the developers.
• Supplies: no study compares bacteriostatic and sterile water for a peptide, and the measured storage data are specific to the compound tested.

Evidence levels follow Prof. Peptide’s four study designs, explained in Peptides 101; they describe how a form was studied, not whether it works. The label figures for approved pills and sprays are set out in peptide pills vs nasal sprays vs injections.

What studies report

• No human study compares subcutaneous with intramuscular injection for BPC-157, TB-500, CJC-1295, ipamorelin, GHK-Cu, semaglutide, tirzepatide or retatrutide. For other injected hormones the two routes gave similar effects with some differences in timing: subcutaneous hCG peaked later and lasted longer, with identical hormone responses1, although a second hCG study measured higher exposure after intramuscular injection2; triptorelin3 and growth hormone4 showed no meaningful route difference. These are hormones and proteins, not short research peptides.
• Dry and dissolved stability has been measured for other peptides only. Lyophilized teriparatide held for months dry, but some reconstituted samples precipitated within 2–4 weeks5; reconstituted sincalide6 and a GHRH analogue7 stayed chemically stable for days to weeks. How long a solution lasts depends on the compound.
• Freezing aggregated growth hormone8 and glucagon9. Light changed compounded semaglutide10, and liraglutide formed fibrils when shaken with air and silicone oil in the vial, which the authors attribute to stress at those surfaces rather than to shear11.
• Three lyophilized semaglutide vials bought from illegal online pharmacies held 28.56–38.69% more semaglutide than labelled, measured 7.7–14.37% purity against a claimed 99%, and contained endotoxin12.

Where evidence is absent

Storage

In Prof. Peptide’s catalog data

Counts are from Prof. Peptide's price data on October 26, 2026: 102 vendor catalogs, 101 of them with at least one single-compound vial. A count says what is listed, not that a product works or is absorbed.

What studies report

• Follow-on and compounded semaglutide and liraglutide carried impurity profiles that differed from the originals, with more potentially immunogenic peptides in a cell assay; light exposure changed compounded semaglutide's strength and impurities10.
• An editorial reviewing 33 compounded semaglutide and tirzepatide listings found that 18% gave a beyond-use date and 28% gave storage conditions; it measured no product13.
• EudraVigilance held 234 reports of suspected counterfeit semaglutide from 2018 to 2025, 89.3% of the suspected reactions serious; spontaneous reports do not establish cause14.
• A preprint testing 6,441 research-market peptide samples reports 41.6–71.1% failing quality criteria, depending on the standard, with endotoxin measurable in 15%; it has not been peer reviewed15.

Where evidence is absent

Storage

In Prof. Peptide’s catalog data

Counts are from Prof. Peptide's price data on October 26, 2026: 102 vendor catalogs, 101 of them with at least one single-compound vial. A count says what is listed, not that a product works or is absorbed.

What studies report

• Oral semaglutide is absorbed in the stomach next to the tablet and depends on its co-formulated enhancer, SNAC, which protects the peptide locally and briefly raises absorption through the stomach cells17. Its modelled bioavailability is 0.8% under the recommended conditions, with 137% within-subject variability18. A meal before the tablet left little or no exposure, 50 mL and 120 mL of water made no difference19, and shorter fasts before the dose cut exposure to 0.12–0.43 of an overnight fast20.
• Octreotide capsules kept responder rates near 90% over three years, but in patients selected for responding to both the capsule and the injection21. Reviews list enzymes, instability and the gut lining as the barriers, and most oral peptide programmes have not reached approval2223.
• Oral BPC-157 healed fistulas in rats given it in drinking water, with no blood levels reported24. A 2026 review describes BPC-157 as stable in gastric juice, but calls its human pharmacokinetics critically undercharacterized16. Stability in the stomach is not the same as absorption into the blood.
• KPV entered human intestinal cells and reduced colitis in mice given it in drinking water; absorption into the blood was not studied25.
• Glutathione, a tripeptide, did not raise plasma levels after one dose of about 3 g26, but raised blood levels over six months of daily dosing in a randomized trial27; the two designs measured different things. Five days of an oral NAD+ formulation (a coenzyme, not a peptide) raised NAD inside blood cells by 53% while plasma NAD did not change28.

Where evidence is absent

Storage

In Prof. Peptide’s catalog data

Counts are from Prof. Peptide's price data on October 26, 2026: 102 vendor catalogs, 101 of them with at least one single-compound vial. A count says what is listed, not that a product works or is absorbed.

What studies report

• Sublingual oxytocin reached 0.007–0.07% of intravenous bioavailability in six men, a ten-fold spread, and the authors judged the route unreliable29.
• Sublingual desmopressin was below the limit of measurement in plasma at doses under 80 µg, with very wide variation between people, in an open exploratory study30.
• A buccal tablet of GLP-1 itself, not semaglutide or tirzepatide, reached 7% of intravenous bioavailability in a double-blind trial in eight volunteers31.
• Sublingual and swallowed NMN, an NAD+ precursor, gave the same blood NMN and NAD+ in a crossover trial32. Of 17 single-ingredient compounded semaglutide or tirzepatide listings, 82% were sublingual products whose efficacy and safety are unknown13.

Where evidence is absent

Storage

In Prof. Peptide’s catalog data

Counts are from Prof. Peptide's price data on October 26, 2026: 102 vendor catalogs, 101 of them with at least one single-compound vial. A count says what is listed, not that a product works or is absorbed.

What studies report

• The device matters: a metered desmopressin spray was absorbed 2–3 times better than drops33. The sermorelin sequence, GHRH(1–29)-NH2, had 3–5% nasal bioavailability in 30 men34.
• Intranasal PT-141 (bremelanotide) peaked at a median 0.5 hours with a half-life of about 2 hours, and erections exceeded placebo at doses over 7 mg35. In 18 women, a single 20 mg dose raised reported desire and arousal satisfaction while vaginal vasocongestion did not change significantly36. A later trial states that 20 mg gives 1–2 times the exposure of the subcutaneous dose then in phase III37.
• Semax was given intranasally to 27 patients with motor neuron disease in an open-label study38. In mice, intranasal and injected Selank changed different receptor binding39.
• Nose-to-brain delivery is not established as a route: intranasal oxytocin raised cerebrospinal-fluid levels in people without tracking blood levels40, gave no cerebrospinal-fluid advantage over intravenous dosing in macaques41, and a review argues very little of a large dose reaches the brain's fluid42. Intranasal insulin, the best-studied case, made no difference over 12 months in 289 people with cognitive impairment43.

Where evidence is absent

Storage

In Prof. Peptide’s catalog data

Counts are from Prof. Peptide's price data on October 26, 2026: 102 vendor catalogs, 101 of them with at least one single-compound vial. A count says what is listed, not that a product works or is absorbed.

What studies report

• A long-standing proposal holds that molecules above 500 daltons do not cross the skin's outer layer; it is a rule drawn from observed allergens and drugs, not an experiment44. The GHK tripeptide is highly water-soluble45, and a review notes it passes poorly through the skin's lipid layer and that liposome carriers have received little study46.
• Prof. Peptide's GHK-Cu profile cites a randomized double-blind trial of a nano-carrier serum in 40 women47. A systematic review finds most GHK-Cu randomized trials small and limited to facial cosmetic creams48, and another review describes a 13-person post-laser study that was negative on objective measures and an 18-person split-face study with positive cosmetic results49.
• AHK-Cu lengthened human hair follicles in the dish, with skin penetration not tested50. A BPC-157 cream improved healing of laser-injured skin in mice, without absorption measured51. A meta-analysis of 19 trials of oral and topical peptides for skin found a modest wrinkle benefit, driven by the oral products52.

Where evidence is absent

Storage

In Prof. Peptide’s catalog data

Counts are from Prof. Peptide's price data on October 26, 2026: 102 vendor catalogs, 101 of them with at least one single-compound vial. A count says what is listed, not that a product works or is absorbed.

What studies report

• A developer-authored report on Epitalon in retinitis pigmentosa gives no group size or control details in its abstract54. The largest human report, 266 older people followed for 6–8 years with lower mortality, used the extracts Thymalin and Epithalamin, not Epitalon55. The only other human report on Epitalon itself, also from the developers, measured night-time melatonin56. An independent review finds no adequately powered randomized trial and inadequate pharmacokinetic and safety data53.
• Epitalon injected under the skin reduced chemically induced tumours in rats57. Cortagen's evidence is a gene-expression screen in mouse heart58. For Cardiogen, a culture of rat heart tissue treated no animal and measured no fibrosis or heart-protection outcome59; the study behind its Animal model level on Prof. Peptide injected it into rats with transplanted sarcoma, where tumour growth slowed60. Epitalon raised telomerase in normal human cell lines and lengthened telomeres in breast-cancer cell lines61.
• On absorption, a developer review says carriers in the gut move mainly two- and three-residue peptides, and reports no blood-level data for any bioregulator62; Epitalon, Cortagen and Cardiogen have four residues.

Where evidence is absent

Storage

In Prof. Peptide’s catalog data

Counts are from Prof. Peptide's price data on October 26, 2026: 102 vendor catalogs, 101 of them with at least one single-compound vial. A count says what is listed, not that a product works or is absorbed.

What studies report

• No study compares a peptide dissolved in bacteriostatic water with the same peptide in sterile water. A review notes that multi-dose protein and peptide products need a preservative, and that some preservatives increase particle formation, so the choice has to suit the peptide63. The one randomized comparison found, of catheter flushes in children, showed no difference in colonisation and did not test a vial64.
• Benzyl alcohol, the preservative in bacteriostatic water, was linked to brain haemorrhage, acidosis and deaths in premature infants under 1,000 g, with survival improving after it was withdrawn65. No study measures adult exposure from a peptide vial.
• Opened multi-dose vials in hospitals were contaminated in 5.5%66 and 5.36%67 of cases, linked to needle reuse and storage; neither study measured whether a preservative helped.
• No study tested running the water down the vial wall, or swirling against shaking. The one agitation study found attributes damage to air and silicone-oil surfaces, not shear11.

Storage

In Prof. Peptide’s catalog data

Counts are from Prof. Peptide's price data on October 26, 2026: 102 vendor catalogs, 101 of them with at least one single-compound vial. A count says what is listed, not that a product works or is absorbed.

1. Pharmacodynamics and pharmacokinetics after subcutaneous and intramuscular injection of human chorionic gonadotropinHuman RCTSaal W, Glowania HJ, Hengst W, Happ J. Fertil Steril. 1991;56(2):225-229.Key finding: 24 healthy men given 5,000 IU of hCG by either route: the subcutaneous dose peaked later and had a longer half-life; testosterone, LH and FSH responses were identical.PubMed 1712735 →DOI →
2. Bioavailability of hCG after intramuscular or subcutaneous injection in obese and non-obese womenHuman observationalChan CC, Ng EH, Chan MM, Tang OS, Lau EY, Yeung WS, et al. Hum Reprod. 2003;18(11):2294-2297.Key finding: A crossover in 24 women: higher hCG exposure (area under the curve and peak) after intramuscular than after subcutaneous injection.PubMed 14585876 →DOI →
3. Intramuscular and subcutaneous gonadotropin-releasing hormone agonist tests for central precocious puberty in girls: a randomized controlled trialHuman RCTLerdrassameethad W, Wacharasindhu S, Supornsilchai V, Srilanchakon K. Clin Exp Pediatr. 2026;69(6):518-523.Key finding: 92 girls tested with triptorelin by either route: the LH response did not differ.PubMed 41986954 →Full text (PMC13244059) →DOI →
4. A comparison of subcutaneous and intramuscular administration of human growth hormone in the therapy of growth hormone deficiencyHuman observationalRusso L, Moore WV. J Clin Endocrinol Metab. 1982;55(5):1003-1006.Key finding: Subcutaneous and intramuscular growth hormone gave similar peak and integrated levels.PubMed 6889608 →DOI →
5. Stability of lyophilized teriparatide, PTH(1-34), after reconstitutionIn vitroMerutka G, Murphy BM, Payne RW, Wilson GA, Matsuura JE, Henry CS, et al. Eur J Pharm Biopharm. 2016;99:84-93.Key finding: Lyophilized teriparatide was stable for months dry; after reconstitution some samples precipitated within 2–4 weeks, depending on concentration and temperature, while samples never lyophilized did not over 12 weeks.PubMed 26620825 →DOI →
6. Chemical Stability of Reconstituted Sincalide in Sterile Water Under 2 Different Storage ConditionsIn vitroBelanger E, Wolf SM, Zatt SA, Christoff J, Rojeab Y. J Nucl Med Technol. 2020;48(2):174-176.Key finding: Reconstituted sincalide showed little or no chemical loss over 8 days at room temperature or refrigerated; the authors state microbial testing would be needed before extended use.PubMed 32111658 →DOI →
7. Investigation of the chemical stability of a new growth hormone-releasing hormone (GHRH) analogue by HPLCIn vitroIdei M, Mezö I, Szabó EZ, Kéri G. Biomed Chromatogr. 1996;10(2):89-91.Key finding: A GHRH(1–30) analogue in solution was stable for 36 days at 4 °C and 28 days at 25 °C by HPLC. An analogue, not sermorelin or tesamorelin.PubMed 8924733 →DOI →
8. Dissolved oxygen effects on human growth hormone stability during freeze-thaw and metal-catalyzed oxidationIn vitroMiyahara Y, Nagel R, Frieß W. J Pharm Sci. 2026;115(8):104316.Key finding: Human growth hormone aggregated during freezing and thawing.PubMed 42097404 →DOI →
9. DSC reveals the excipient impact on aggregation propensity of pharmaceutical peptides during freezingIn vitroZäh M, Brandenbusch C, Artusio F, Sadowski G, Pisano R. Eur J Pharm Sci. 2025;204:106954.Key finding: Glucagon aggregated on repeated freeze–thaw cycles in this laboratory study.PubMed 39489188 →DOI →
10. Impurities and Potential Immunogenicity Associated With Follow-on and Compounded Glucagon-like Peptide-1 Receptor AgonistsIn vitroKopp KL, Lamberth K, Schelde O, Øgendahl AK, Wojcieszek M, Mogensen JE, et al. Pharm Res. 2026;43(8):2861-2886.Key finding: Follow-on and compounded semaglutide and liraglutide had distinct impurity profiles and more potentially immunogenic peptides in a dendritic-cell assay; after light exposure, compounded semaglutide differed in strength and impurities.PubMed 42533250 →Full text (PMC13593678) →DOI →
11. Molecular Mechanisms of Liraglutide Aggregation Induced by Dual Air-Water and Silicone-Oil-Water Interfacial StressIn vitroHamada N, Cutts A, Song J, Hu G, Fu D, Wuelfing WP, et al. Mol Pharm. 2026;23(2):1295-1309.Key finding: Liraglutide fibrillated under agitation with air headspace and a silicone-oil interface; mild agitation with little headspace changed little. The authors attribute the damage to interfacial stress, not shear.PubMed 41572471 →DOI →
12. Multifactor Quality and Safety Analysis of Semaglutide Products Sold by Online Sellers Without a Prescription: Market Surveillance, Content Analysis, and Product Purchase Evaluation StudyIn vitroAshraf AR, Mackey TK, Vida RG, Kulcsár G, Schmidt J, Balázs O, et al. J Med Internet Res. 2024;26:e65440.Key finding: Three lyophilized semaglutide vials bought from illegal online pharmacies: no viable microorganisms at testing, but endotoxin of 2.16–8.95 EU/mg, content 28.56–38.69% above the label amount, and measured purity of 7.7–14.37% against a claimed 99%.PubMed 39509151 →Full text (PMC11582493) →DOI →
13. Compounded Semaglutide and Tirzepatide Products Use Unique Formulations but Efficacy and Safety Largely UnknownEditorialBelcourt J, Sapowadia A, White CM. Ann Pharmacother. 2026;60(9):902-906.Key finding: A web search found 33 compounded semaglutide or tirzepatide products; of the 17 single-ingredient ones, 82% were sublingual and 18% orally disintegrating tablets. 18% listed a beyond-use date and 28% storage conditions. No product content was measured.PubMed 41689811 →DOI →
14. Unmasking counterfeit semaglutide: analysis of real-world safety data from EudraVigilanceHuman observationalZinzi A, Gaio M, Ruggiero R, Mascolo A, Riemma MA, Cipriani M, et al. Front Pharmacol. 2026;17:1805842.Key finding: 234 EudraVigilance reports of suspected counterfeit semaglutide, 2018–2025; 89.3% of the suspected reactions were serious. Spontaneous reports do not establish cause.PubMed 42137313 →Full text (PMC13168152) →DOI →
15. Evaluation of Research Grade Peptides Marketed Directly to Consumers Reveals Extensive Variability in Purity and Measured AbundancePreprintMendias CL, Awan TM. Preprints.org. 2026. Not peer reviewed.Key finding: 6,441 research-market peptide samples: 41.6–71.1% failed quality criteria, depending on the standard applied, and endotoxin was measurable in 15%. Not peer reviewed; how samples were selected is not described in the abstract.DOI →
16. BPC-157 as an Investigational Peptide Therapeutic: Biopharmaceutical Challenges, Formulation Strategies, and Translational Development BarriersReviewMateescu DM, Gavrilescu DM, Constantinescu FE, Oancea C, Ilie AC, Folescu R, et al. Pharmaceutics. 2026;18(5):625.Key finding: Describes BPC-157 as stable in gastric juice and active by several routes in animals; human pharmacokinetics are critically undercharacterized, clinical data come from fewer than 30 subjects in three uncontrolled pilots, and no pharmaceutical-grade formulation has been validated.PubMed 42198317 →Full text (PMC13210877) →DOI →
17. Transcellular stomach absorption of a derivatized glucagon-like peptide-1 receptor agonistHuman and animal studyBuckley ST, Bækdal TA, Vegge A, Maarbjerg SJ, Pyke C, Ahnfelt-Rønne J, et al. Sci Transl Med. 2018;10(467):eaar7047.Key finding: Oral semaglutide is absorbed in the stomach next to the tablet and depends on its co-formulated SNAC, which protects it locally and briefly raises absorption through the cells; no effect on the junctions between cells was found.PubMed 30429357 →DOI →
18. Clinical Pharmacokinetics of Oral Semaglutide: Analyses of Data from Clinical Pharmacology TrialsHuman observationalOvergaard RV, Navarria A, Ingwersen SH, Bækdal TA, Kildemoes RJ. Clin Pharmacokinet. 2021;60(10):1335-1348.Key finding: Population pharmacokinetics from six trials: modelled bioavailability of 0.8% under the recommended conditions, with 137% within-subject variability; exposure rose with longer fasting after the dose and fell with more water.PubMed 33969456 →Full text (PMC8505367) →DOI →
19. Effect of Various Dosing Conditions on the Pharmacokinetics of Oral Semaglutide, a Human Glucagon-Like Peptide-1 Analogue in a Tablet FormulationHuman RCTBækdal TA, Breitschaft A, Donsmark M, Maarbjerg SJ, Søndergaard FL, Borregaard J. Diabetes Ther. 2021;12(7):1915-1927.Key finding: A meal before the dose left little or no exposure; 50 mL and 120 mL of water made no difference; longer fasting after the dose raised exposure.PubMed 34080123 →Full text (PMC8266944) →DOI →
20. Effect of Various Dosing Schedules on the Pharmacokinetics of Oral Semaglutide: A Randomised Trial in Healthy SubjectsHuman RCTvan Hout M, Forte P, Jensen TB, Boschini C, Bækdal TA. Clin Pharmacokinet. 2023;62(4):635-644.Key finding: 156 participants: shorter fasts before the dose gave lower exposure than an overnight fast (AUC ratios 0.12–0.43).PubMed 36932262 →Full text (PMC10023024) →DOI →
21. MPOWERED Trial Open-Label Extension: Long-term Efficacy and Safety Data for Oral Octreotide Capsules in AcromegalyHuman RCTFleseriu M, Molitch M, Dreval A, Pokramovich Y, Bondar I, Poteshkin Y, et al. J Clin Endocrinol Metab. 2023;108(12):3214-3222.Key finding: Octreotide capsules, open-label extension: responder rates of 89.7%, 87.8% and 93.5% at years 1–3, in patients selected for responding to both the capsule and injected octreotide or lanreotide. An efficacy extension, not an absorption measurement.PubMed 37319438 →Full text (PMC10655542) →DOI →
22. Barriers and Strategies for Oral Peptide and Protein Therapeutics Delivery: Update on Clinical AdvancesReviewBaral KC, Choi KY. Pharmaceutics. 2025;17(4):397.Key finding: Enzymatic breakdown, instability and poor passage across the gut lining limit swallowed peptides and proteins.PubMed 40284395 →Full text (PMC12030352) →DOI →
23. Oral delivery of peptides and proteins: pharmacokinetic boundaries, negative selection, and route triageReviewNiazi SK. Front Drug Deliv. 2026;6:1776167.Key finding: Enteric coatings, enzyme inhibitors, permeation enhancers and nanoparticles have each been tried, and most oral peptide programmes did not reach approval.PubMed 41939723 →Full text (PMC13047097) →DOI →
24. Pentadecapeptide BPC 157, in clinical trials as a therapy for inflammatory bowel disease (PL14736), is effective in the healing of colocutaneous fistulas in rats: role of the nitric oxide-systemAnimal modelKlicek R, Sever M, Radic B, Drmic D, Kocman I, Zoricic I, et al. J Pharmacol Sci. 2008;108(1):7-17.Key finding: Rats with colocutaneous fistulas given BPC-157 in drinking water or by intraperitoneal injection healed faster by either route; the abstract reports no blood levels.PubMed 18818478 →DOI →
25. PepT1-mediated tripeptide KPV uptake reduces intestinal inflammationAnimal modelDalmasso G, Charrier-Hisamuddin L, Nguyen HT, Yan Y, Sitaraman S, Merlin D. Gastroenterology. 2008;134(1):166-178.Key finding: KPV entered human intestinal cells through the PepT1 transporter and reduced inflammatory signalling; mice with colitis given KPV in drinking water had less colitis. Absorption into the blood was not studied.PubMed 18061177 →Full text (PMC2431115) →DOI →
26. The systemic availability of oral glutathioneHuman observationalWitschi A, Reddy S, Stofer B, Lauterburg BH. Eur J Clin Pharmacol. 1992;43(6):667-669.Key finding: Seven volunteers given one oral dose of about 3 g: no significant rise in plasma glutathione over 270 minutes; the authors call systemic availability negligible.PubMed 1362956 →DOI →
27. Randomized controlled trial of oral glutathione supplementation on body stores of glutathioneHuman RCTRichie JP, Nichenametla S, Neidig W, Calcagnotto A, Haley JS, Schell TD, et al. Eur J Nutr. 2015;54(2):251-263.Key finding: 54 adults given 250 or 1,000 mg a day for 6 months: blood glutathione rose at 1, 3 and 6 months.PubMed 24791752 →DOI →
28. Oral LNAD+ rapidly elevates whole blood intracellular NAD and metabolic flux without elevating plasma NAD: evidence from a randomized controlled trialHuman RCTKornilov SA, Hastings WJ, McGrath LF, Leitz-Langan M, Magis AT, Coppess SM, et al. Geroscience. 2026.Key finding: 60 adults aged 45–75, 5 days of an oral NAD+ formulation against placebo: whole-blood intracellular NAD rose 53% and plasma NAD did not change. Retrospectively registered.PubMed 42530810 →DOI →
29. Bioavailability and pharmacokinetics of sublingual oxytocin in male volunteersHuman observationalDe Groot AN, Vree TB, Hekster YA, Pesman GJ, Sweep FC, Van Dongen PJ, et al. J Pharm Pharmacol. 1995;47(7):571-575.Key finding: Six men: sublingual oxytocin reached 0.007–0.07% of intravenous bioavailability, a ten-fold spread; the authors judged the route unreliable.PubMed 8568623 →DOI →
30. Plasma pharmacokinetics of desmopressin following sublingual administration: an exploratory dose-escalation study in healthy male volunteersHuman observationalSteiner IM, Kaehler ST, Sauermann R, Rinösl H, Müller M, Joukhadar C. Int J Clin Pharmacol Ther. 2006;44(4):172-179.Key finding: An open, exploratory dose-escalation in 16 healthy men, sublingual desmopressin 20–320 µg: plasma levels were below quantification under 80 µg and varied very widely between people.PubMed 16625986 →DOI →
31. Potential therapeutic levels of glucagon-like peptide I achieved in humans by a buccal tabletHuman RCTGutniak MK, Larsson H, Heiber SJ, Juneskans OT, Holst JJ, Ahrén B. Diabetes Care. 1996;19(8):843-848.Key finding: Eight volunteers, double-blind: a buccal tablet of GLP-1 itself reached 7% of intravenous and 47% of subcutaneous bioavailability.PubMed 8842602 →DOI →
32. Sublingual NMN administration increases early circulating terminal catabolites 2PY and 4PY compared with oral administration in healthy adult menHuman RCTWakabayashi J, Higashi S, Morifuji M. Sci Rep. 2026;16(1):27464.Key finding: 14 men, single doses in a crossover: sublingual and swallowed NMN produced no difference in blood NMN, nicotinamide or NAD+.PubMed 42304075 →Full text (PMC13534420) →DOI →
33. Intranasal administration of peptides: nasal deposition, biological response, and absorption of desmopressinHuman observationalHarris AS, Nilsson IM, Wagner ZG, Alkner U. J Pharm Sci. 1986;75(11):1085-1088.Key finding: Gamma scintigraphy: a metered desmopressin spray was absorbed 2–3 times better than drops.PubMed 3102719 →DOI →
34. Pharmacokinetics of growth hormone-releasing hormone(1-29)-NH2 and stimulation of growth hormone secretion in healthy subjects after intravenous or intranasal administrationHuman observationalWilton P, Chardet Y, Danielson K, Widlund L, Gunnarsson R. Acta Paediatr Suppl. 1993;388:10-15.Key finding: 30 healthy men: intranasal GHRH(1–29)-NH2, the sermorelin sequence, had 3–5% bioavailability; about 50 µg/kg intranasally matched the growth-hormone response of 1 µg/kg intravenously.PubMed 8329825 →DOI →
35. Double-blind, placebo-controlled evaluation of the safety, pharmacokinetic properties and pharmacodynamic effects of intranasal PT-141, a melanocortin receptor agonist, in healthy males and patients with mild-to-moderate erectile dysfunctionHuman RCTDiamond LE, Earle DC, Rosen RC, Willett MS, Molinoff PB. Int J Impot Res. 2004;16(1):51-59.Key finding: Intranasal bremelanotide (PT-141): median time to peak 0.5 h and half-life 1.85–2.09 h; erections above placebo at doses over 7 mg; flushing and nausea were the most common effects.PubMed 14963471 →DOI →
36. An effect on the subjective sexual response in premenopausal women with sexual arousal disorder by bremelanotide (PT-141), a melanocortin receptor agonistHuman RCTDiamond LE, Earle DC, Heiman JR, Rosen RC, Perelman MA, Harning R. J Sex Med. 2006;3(4):628-638.Key finding: 18 premenopausal women, one 20 mg intranasal dose: more reported moderate or high desire and greater arousal satisfaction; vaginal vasocongestion did not change significantly.PubMed 16839319 →DOI →
37. Phase I Randomized Placebo-controlled, Double-blind Study of the Safety and Tolerability of Bremelanotide Coadministered With Ethanol in Healthy Male and Female ParticipantsHuman RCTClayton AH, Lucas J, DeRogatis LR, Jordan R. Clin Ther. 2017;39(3):514-526.e14.Key finding: 24 adults: 20 mg intranasal with or without alcohol was tolerated; the authors state the dose gives about 1–2 times the exposure of the subcutaneous dose then in phase III, which the abstract does not state.PubMed 28189361 →DOI →
38. The study of chronic partial denervation and quality of life in patients with motor neuron disease treated with semaxHuman observationalSerdiuk AV, Levitskiĭ GN, Miasoedov NF, Skvortsova VI. Zh Nevrol Psikhiatr Im S S Korsakova. 2007;107(4):29-39.Key finding: 27 patients with motor neuron disease given Semax 1% solution intranasally in two 10-day courses; the abstract describes the study as open-label.PubMed 18379501 →
39. COMPARISON OF PHARMACOLOGICAL EFFECTS OF HEPTAPEPTIDE SELANK AFTER INTRANASAL AND INTRAPERITONEAL ADMINISTRATION TO BALB/c AND C57BL/6 MICE.Animal modelVasil'eva EV, Kondrakhin EA, Salimov RM, Kovalev GI. Eksp Klin Farmakol. 2016;79(9):3-11.Key finding: Mice given Selank for 5 days intranasally or by intraperitoneal injection: the two routes changed different receptor binding.PubMed 29787664 →
40. Elevated cerebrospinal fluid and blood concentrations of oxytocin following its intranasal administration in humansHuman RCTStriepens N, Kendrick KM, Hanking V, Landgraf R, Wüllner U, Maier W, et al. Sci Rep. 2013;3:3440.Key finding: 24 IU of intranasal oxytocin raised plasma and cerebrospinal-fluid oxytocin, with no correlation between the two.PubMed 24310737 →Full text (PMC3853684) →DOI →
41. Oxytocin by intranasal and intravenous routes reaches the cerebrospinal fluid in rhesus macaques: determination using a novel oxytocin assayAnimal modelLee MR, Scheidweiler KB, Diao XX, Akhlaghi F, Cummins A, Huestis MA, et al. Mol Psychiatry. 2018;23(1):115-122.Key finding: Six macaques: intranasal oxytocin gave no cerebrospinal-fluid advantage over intravenous oxytocin.PubMed 28289281 →Full text (PMC5862033) →DOI →
42. Intranasal Oxytocin: Myths and DelusionsReviewLeng G, Ludwig M. Biol Psychiatry. 2016;79(3):243-250.Key finding: Argues that very little of a large intranasal oxytocin dose appears to reach the cerebrospinal fluid.PubMed 26049207 →DOI →
43. Safety, Efficacy, and Feasibility of Intranasal Insulin for the Treatment of Mild Cognitive Impairment and Alzheimer Disease Dementia: A Randomized Clinical TrialHuman RCTCraft S, Raman R, Chow TW, Rafii MS, Sun CK, Rissman RA, et al. JAMA Neurol. 2020;77(9):1099-1109.Key finding: 289 people with mild cognitive impairment or Alzheimer's disease given 40 IU of intranasal insulin for 12 months: no difference on the main cognitive or cerebrospinal-fluid outcomes.PubMed 32568367 →Full text (PMC7309571) →DOI →
44. The 500 Dalton rule for the skin penetration of chemical compounds and drugsReviewBos JD, Meinardi MM. Exp Dermatol. 2000;9(3):165-169.Key finding: Proposes, from observed allergens and drugs, that molecules above 500 daltons do not cross the skin's outer layer. A proposed rule, not an experiment.PubMed 10839713 →DOI →
45. Physicochemical characterization of native glycyl-l-histidyl-l-lysine tripeptide for wound healing and anti-aging: a preformulation study for dermal deliveryIn vitroBadenhorst T, Svirskis D, Wu Z. Pharm Dev Technol. 2016;21(2):152-160.Key finding: Preformulation study: the GHK tripeptide measured as highly water-soluble (log D −2.38 to −2.49 at pH 4.5–7.4).PubMed 25384620 →DOI →
46. Are We Ready to Measure Skin Permeation of Modern Antiaging GHK-Cu Tripeptide Encapsulated in Liposomes?ReviewOgórek K, Nowak K, Wadych E, Ruzik L, Timerbaev AR, Matczuk M. Molecules. 2025;30(1):136.Key finding: GHK-Cu passes poorly through the skin's lipid outer layer, and transport of GHK-Cu in liposomes has received little study.PubMed 39795193 →Full text (PMC11721469) →DOI →
47. Effects of GHK-Cu on MMP and TIMP Expression, Collagen and Elastin Production, and Facial Wrinkle ParametersHuman RCTBadenhorst T, Svirskis D, Merrilees M, Bolke L, Wu Z. J Aging Sci. 2016;4:166.Key finding: A randomized, double-blind trial of a nano-carrier GHK-Cu serum in 40 women over 8 weeks, as cited on Prof. Peptide's GHK-Cu profile. Not indexed in Europe PMC; its figures were not re-checked for this guide.DOI →
48. A Systematic Review of the Mechanisms and Therapeutic Applications of GHK-Cu (Glycyl-L-Histidyl-L-Lysine-Copper Complex) in Topical Microneedle Delivery: A Case for Expanded Clinical TrialsSystematic reviewNajafi N, Maatouk H, Vardanyan KG, Vartanian KB, Agrawal DK. Arch Intern Med Res. 2026;9(3):269-293.Key finding: Across 64 GHK-Cu records, most randomized trials were small and tested facial cosmetic creams; microneedle GHK-Cu has not been tested in a registered, adequately powered human randomized trial.PubMed 42787770 →Full text (PMC13604022) →DOI →
49. GHK-Cu as a Bioactive Metallopeptide and Drug-Delivery Cargo: Coordination Chemistry, Formulation Science, Therapeutic Evidence, and a Translational RoadmapReviewMateescu DM, Gavrilescu DM, Mincioaga RI, Pah AM, Toma AO, Serban DV, et al. Pharmaceutics. 2026;18(9):1077.Key finding: Describes GHK-Cu clinical evidence as sparse, including a 13-participant post-laser study that was negative on objective endpoints and an 18-participant split-face study with positive cosmetic outcomes.PubMed 42797253 →Full text (PMC13610439) →DOI →
50. The effect of tripeptide-copper complex on human hair growth in vitroIn vitroPyo HK, Yoo HG, Won CH, Lee SH, Kang YJ, Eun HC, et al. Arch Pharm Res. 2007;30(7):834-839.Key finding: AHK-Cu lengthened human hair follicles ex vivo and increased dermal papilla cell growth; skin penetration was not tested.PubMed 17703734 →DOI →
51. The stable gastric pentadecapeptide BPC 157, given locally, improves CO2 laser healing in miceAnimal modelBilic M, Bumber Z, Blagaic AB, Batelja L, Seiwerth S, Sikiric P. Burns. 2005;31(3):310-315.Key finding: Mice with CO₂-laser skin injuries: a BPC-157 cream improved healing at 1, 7 and 21 days. Absorption was not measured, and the skin was injured.PubMed 15774286 →DOI →
52. Oral and topical peptides for skin aging: systematic review and meta-analysis of randomized controlled trialsSystematic reviewNukaly HY, Halawani IR, Irtaza HM, Alturkistani T, Serafi MR, Alhawsawi W, et al. Front Med (Lausanne). 2026;13:1618306.Key finding: Meta-analysis of 19 randomized trials (1,341 participants) of oral and topical peptides for skin: a modest pooled wrinkle benefit, driven by oral polypeptides.PubMed 41924746 →Full text (PMC13037056) →DOI →
53. Epitalon and Epithalamin: A Narrative Review of Mechanistic, Preclinical, and Clinical EvidenceReviewJain A, Gallacher DM, Issa MA, Deer TR, Yong RJ, Diwan S, et al. Int J Mol Sci. 2026;27(19):8922.Key finding: Independent review: Epitalon was synthesised from the amino-acid composition of the pineal extract Epithalamin and is chemically distinct from it; human evidence is limited to small physiological or biomarker studies and an older retinitis pigmentosa study, and no adequately powered randomized trial has established efficacy.PubMed 42884164 →Full text (PMC13664938) →DOI →
54. Pineal-regulating tetrapeptide epitalon improves eye retina condition in retinitis pigmentosaHuman observationalKhavinson V, Razumovsky M, Trofimova S, Grigorian R, Razumovskaya A. Neuro Endocrinol Lett. 2002;23(4):365-368.Key finding: Epitalon in retinitis pigmentosa: a positive clinical effect reported in 90%; group size and control details are not in the abstract. Written by the developers.PubMed 12195242 →
55. Peptides of pineal gland and thymus prolong human lifeHuman observationalKhavinson VKh, Morozov VG. Neuro Endocrinol Lett. 2003;24(3-4):233-240.Key finding: 266 older people followed for 6–8 years: mortality 1.6–4.1 times lower with the preparations, which were the organ extracts Thymalin and Epithalamin, not synthetic Epitalon. Europe PMC tags it a randomized trial; the abstract does not describe randomisation.PubMed 14523363 →
56. Normalizing effect of the pineal gland peptides on the daily melatonin rhythm in old monkeys and elderly peopleHuman observationalKorkushko OV, Lapin BA, Goncharova ND, Khavinson VKh, Shatilo VB, Vengerin AA, et al. Adv Gerontol. 2007;20(1):74-85.Key finding: Epithalamin and Epitalon raised night-time melatonin in older people and in old monkeys.PubMed 17969590 →
57. Inhibitory effect of peptide Epitalon on colon carcinogenesis induced by 1,2-dimethylhydrazine in ratsAnimal modelAnisimov VN, Khavinson VKh, Popovich IG, Zabezhinski MA. Cancer Lett. 2002;183(1):1-8.Key finding: Epitalon, 1 µg injected under the skin 5 days a week, cut tumours per rat from 4.1 to 2.7 in a chemically induced colon-cancer model.PubMed 12049808 →DOI →
58. Elucidation of the effect of brain cortex tetrapeptide Cortagen on gene expression in mouse heart by microarrayAnimal modelAnisimov SV, Khavinson VKh, Anisimov VN. Neuro Endocrinol Lett. 2004;25(1-2):87-93.Key finding: Cortagen changed 234 of 15,247 gene clones in mouse heart in a microarray screen; no functional outcome was measured.PubMed 15159690 →
59. The effect of the amino acids and cardiogen on the development of myocard tissue culture from young and old ratsIn vitroChalisova NI, Lesniak VV, Balykina NA, Urt'eva SA, Urt'eva TA, Sukhonos IuA, et al. Adv Gerontol. 2009;22(3):409-413.Key finding: Cardiogen at 10⁻¹² M increased cell growth and lowered p53 staining in cultured rat heart-tissue explants. No animal was treated, and no fibrosis or heart-protection outcome was measured.PubMed 20210190 →
60. Tumor-modifying effect of cardiogen peptide on M-1 sarcoma in senescent ratsAnimal modelLevdik NV, Knyazkin IV. Bull Exp Biol Med. 2009;148(3):433-436.Key finding: Rats with transplanted M-1 sarcoma given Cardiogen injections: tumour-cell apoptosis was higher than in controls and tumour growth was inhibited in a dose-dependent way, through the tumour's blood vessels rather than a direct cytostatic effect.PubMed 20396706 →DOI →
61. Epitalon increases telomere length in human cell lines through telomerase upregulation or ALT activityIn vitroAl-Dulaimi S, Thomas R, Matta S, Roberts T. Biogerontology. 2025;26(5):178.Key finding: Epitalon raised telomerase and telomere length in normal human cell lines and lengthened telomeres in breast-cancer cell lines through the ALT pathway.PubMed 40908429 →Full text (PMC12411320) →DOI →
62. Transport of Biologically Active Ultrashort Peptides Using POT and LAT CarriersReviewKhavinson V, Linkova N, Kozhevnikova E, Dyatlova A, Petukhov M. Int J Mol Sci. 2022;23(14):7733.Key finding: Developer review: carriers of the POT family move mainly di- and tripeptides into cells. It reports no oral bioavailability or blood-level data for any bioregulator.PubMed 35887081 →Full text (PMC9323678) →DOI →
63. Antimicrobial Preservatives for Protein and Peptide Formulations: An OverviewReviewStroppel L, Schultz-Fademrecht T, Cebulla M, Blech M, Marhöfer RJ, Selzer PM, et al. Pharmaceutics. 2023;15(2):563.Key finding: Multi-dose protein and peptide products need antimicrobial preservatives, and some preservatives increase particle formation, so the preservative has to suit the active ingredient.PubMed 36839885 →Full text (PMC10217790) →DOI →
64. Bacterial colonization of tunneled right atrial catheters in pediatric oncology: a comparison of sterile saline and bacteriostatic saline flush solutionsHuman RCTWiernikowski JT, Elder-Thornley D, Dawson S, Rothney M, Smith S. Am J Pediatr Hematol Oncol. 1991;13(2):137-140.Key finding: Children's catheters flushed with sterile or bacteriostatic saline for 26 weeks: colonisation rates did not differ significantly. Not a test of a peptide vial.PubMed 2069220 →DOI →
65. Benzyl alcohol toxicity in a neonatal intensive care unit. Incidence, symptomatology, and mortalityHuman observationalMenon PA, Thach BT, Smith CH, Landt M, Roberts JL, Hillman RE, et al. Am J Perinatol. 1984;1(4):288-292.Key finding: Neonatal-unit infants under 1,000 g with raised blood benzyl alcohol had more intraventricular haemorrhage, metabolic acidosis and deaths than weight-matched controls; survival improved after benzyl-alcohol solutions were stopped.PubMed 6440575 →DOI →
66. Bacterial contamination of single and multiple-dose parenteral injection vials after opening and antibiotic susceptibility of isolates at Jimma Medical Center, Jimma, Southwest EthiopiaHuman observationalTabor A, Shalemariam Z, Alemu Y, Gorems K. Infect Prev Pract. 2023;5(3):100290.Key finding: 5.5% of 384 opened multiple-dose hospital vials were contaminated, and none of the single-dose vials, linked to syringe and needle reuse and to storage.PubMed 37457638 →Full text (PMC10339008) →DOI →
67. Microbial contamination of single- and multiple-dose vials after opening in a pulmonary teaching hospitalHuman observationalBaniasadi S, Dorudinia A, Mobarhan M, Karimi Gamishan M, Fahimi F. Braz J Infect Dis. 2013;17(1):69-73.Key finding: 5.36% of 205 opened vials were contaminated, most often insulin, mainly with Staphylococcus epidermidis.PubMed 23294643 →Full text (PMC9427349) →DOI →

Study details are as printed in each abstract, read through Europe PMC on October 26, 2026; full texts were not read. Grades are Prof. Peptide’s study-design levels.