Where to Buy PT-141: 7 Purity and Identity Checks for a Peptide One Dalton From an Unapproved Drug

PT-141 is the only FDA-approved compound in this category, and the hardest one in it to verify. Bremelanotide sits about one dalton from melanotan II, a substance approved in no country, and no routine purity test can separate them.

That gap governs the whole buying decision. PT-141 sits in the libido and sexual wellness peptides category, and the evidence picture — two phase 3 trials in 1,267 women that moved desire scores about 0.3 points while leaving satisfying sexual events unchanged — is in PT-141: the desire scores moved, the satisfying sexual events did not. For converting a reconstituted vial into an injection volume there is the peptide dosing calculator.

What is PT-141, and why does source quality matter?

PT-141 is a cyclic heptapeptide analogue of α-MSH — Ac-Nle-cyclo-(Asp-His-D-Phe-Arg-Trp-Lys-OH), CAS 189691-06-3, molecular weight 1,025.2 g/mol — approved as VYLEESI under NDA 210557 on 21 June 2019. Source quality matters differently here because the nearest substitute is not a degradation product: melanotan II shares the identical backbone and lactam bridge and differs only at the C-terminus, 1,024.18 against 1,025.2. That is an approved drug and a substance approved nowhere, separated by one terminal group.

The molecule is built from the α-MSH "message" core — the His-Phe-Arg-Trp pharmacophore — with a norleucine at position 4, a D-phenylalanine at position 7, and a side-chain-to-side-chain lactam bridge from Asp5 to Lys10 that closes the ring. Every one of those features is shared with melanotan II. The only structural difference between the two is the C-terminal group: a free acid on bremelanotide, a lysine amide on melanotan II.

A separation of about 1.0 dalton on 1,025 daltons is under 0.1%, which is below what HPLC purity testing or nominal-mass mass spectrometry can resolve. That single fact reorganises the whole buying process for this compound. Purity measures how much of a sample is one thing; it says nothing about which thing. On most peptides the certificate answers the important question. Here it answers a different one. Vendor coverage and identity references sit on the PT-141 compound page.

What is the regulatory status of PT-141?

PT-141 is an FDA-approved prescription drug, approved as VYLEESI on 21 June 2019 under NDA 210557, currently marketed by Cosette Pharmaceuticals, for acquired, generalised hypoactive sexual desire disorder in premenopausal women only. As of August 2026 bremelanotide is not named on the WADA 2026 Prohibited List, and the S0 catch-all — which captures substances with "no current approval by any governmental regulatory health authority" — does not obviously reach an approved drug. The label rules out men and performance.

The approved product is a 1.75 mg base / 0.3 mL subcutaneous autoinjector, prescription only, with no boxed warning. The application originated with AMAG Pharmaceuticals, rights returned to Palatin on 27 July 2020, and Cosette Pharmaceuticals acquired it on 3 January 2024.

The Limitations of Use are two sentences long and they exclude essentially the entire grey-market use case. In FDA's exact words: "Not indicated for treatment of HSDD in postmenopausal women or in men." And: "Not indicated to enhance sexual performance."

The dosing limits are equally specific: one 1.75 mg subcutaneous injection to the abdomen or thigh, at least 45 minutes before anticipated sexual activity, no more than one dose in 24 hours, and "More than 8 doses per month is not recommended." There is no annual cap in the label. That figure circulates online and it is not in the document. The contraindication is uncontrolled hypertension or known cardiovascular disease, and the label adds that VYLEESI "is not recommended for patients at high risk for cardiovascular disease."

Bremelanotide does not appear on FDA's list of bulk substances that may present significant safety risks. Our FDA peptide regulation timeline tracks how those lists have moved.

How do you tell PT-141 from melanotan II?

High-resolution mass spectrometry or MS/MS fragmentation, and nothing cheaper. PT-141 at 1,025.2 Da and melanotan II at 1,024.18 differ by about 1.0 Da on 1,025, under 0.1%, so they co-elute on HPLC and nominal-mass MS cannot resolve them reliably. The risk runs one way on this compound: someone ordering bremelanotide can receive melanotan II, a substance approved in no country, while the reverse substitution costs a melanotan II buyer nothing.

That asymmetry is the reason this section exists on the PT-141 page and reads differently on the melanotan II buying page. A PT-141 buyer is paying for the regulatory pedigree — the approval, the label, the dose limits, the manufacturing chain behind an approved application. A substituted vial removes all of it while producing a flawless purity certificate.

There is a published forensic literature on exactly this substitution, and its existence is the argument. Mestria et al. (Drug Testing and Analysis, 2021) characterised black-market melanotan II and bremelanotide by LC-HRMS, and Breindahl et al. (Drug Testing and Analysis, 2015) identified and characterised melanotan II products sold illegally online. Forensic chemists do not develop high-resolution methods for markets without a discrimination problem. See mass spectrometry for peptides for what resolution actually buys you.

The practical instruction is narrow. Ask whether the mass spectrometry on the certificate is high-resolution or nominal-mass, and whether it was run on your batch. A nominal-mass instrument reporting "1,025" is reporting a number it cannot defend to the decimal that matters.

7 things to check before ordering PT-141

Seven checks cover PT-141, and only the first one resolves the identity question. High-resolution mass spectrometry at 1,025.2 Da, the salt form on a drug substance defined as bremelanotide acetate with one to two acetate equivalents, third-party HPLC against a 99.70% benchmark, net peptide content, fill accuracy against a recorded range of −3.3% to +16.3%, an LAL endotoxin result absent from most entries, and a pricing check read inside a single vial-size band.

1. High-resolution MS or MS/MS fragmentation at 1,025.2 Da. This is the only check that establishes which molecule you have. Nominal-mass MS cannot separate 1,025.2 from 1,024.18, and HPLC co-elutes them. Ask for the instrument type and a batch-matched result, not a specimen certificate from an earlier lot, which describes a different vial.

2. Salt form, stated explicitly. The approved drug substance is bremelanotide acetate, C₅₀H₆₈N₁₄O₁₀ · xCH₃COOH with 1 ≤ x ≤ 2, so a certificate that does not say whether it is quoting free base or acetate is quoting a mass you cannot use. The confusion compounds here: the free acid versus lysine amide distinction is the identity question, and the acetate counter-ion is a separate axis on top of it. See TFA versus acetate versus amidate salt forms.

3. Third-party HPLC purity from a named laboratory — and what it does not establish. This platform records 99.70% across 242 independent tests, so "above 98%" describes a standard the market already clears. A vendor's own document is not third-party testing (third-party peptide testing labs), and even a perfect result is a homogeneity measurement (what HPLC testing measures).

4. Net peptide content. Purity reports the proportion of a sample that is one species; net content reports how much peptide is in the vial, with acetate salt and residual water sitting inside the difference. Ask for a net content or amino acid analysis figure separately (why 10 mg isn't 10 mg).

5. Fill accuracy, against a documented +16.3%. Quantity variance on this platform's PT-141 data runs −3.3% to +16.3%, and two vendors returned the top figure: a 30 mg label that tested at 34.9 mg, and a 10 mg label that tested at 11.63 mg. A fill process running 16% over is a fill process that is not being measured, and the same process underfills.

6. An LAL endotoxin result. Endotoxin results are mostly absent on PT-141. A blank field means the batch was not tested for pyrogens rather than that it passed, and this is injectable material. See peptide endotoxin testing and the LAL assay.

7. The pricing check, read within a vial-size band — and what no certificate establishes. Listings run $2.00/mg on a 10 mg vial to $9.59/mg on a 5 mg vial, so a per-milligram comparison across sizes is not like-for-like. Beyond that, a flawless certificate confirms a cyclic heptapeptide at a stated quantity. It does not tell you the label limits dosing to 8 doses per month, that focal hyperpigmentation runs 1% inside that cap and 38% after eight daily doses, or that the endpoint counting actual sexual encounters showed "no significant difference between treatment groups." See red flags in peptide certificates of analysis.

Where does PT-141 rank on Peptigrity's lab test database?

Peptigrity's Purity Index records PT-141 at 99.70% across 242 independent HPLC tests from Freedom Diagnostics, ILS, Kovera, Accurate Test Lab, MZ Biolabs and Ethos Analytics, across 225 verified shops (verified August 2026), with testing current to late July 2026. Price data shows 65 shops in stock at a median of $4.40 per milligram, lowest $2.00/mg on a 10 mg vial and highest $9.59/mg on a 5 mg vial (verified 10 August 2026). Quantity variance runs −3.3% to +16.3%.

Those figures exclude shipping, taxes and customs, coupon codes, bulk tiers, multi-vial kits and account-gated pricing.

Two flags sit in the PT-141 data and both are about quantity rather than identity, because identity is not something this dataset can flag. The two +16.3% overages are the first, and the measured fills are worth carrying: a 30 mg label tested at 34.9 mg and a 10 mg label at 11.63 mg. Endotoxin results are mostly absent is the second. Naming the six laboratories matters for the same reason: a reader can weigh where 242 tests came from rather than take a bare percentage, and can search the lab test database and community-verified shop reviews for a specific vendor rather than relying on a compound-level average. Peptigrity tracks 530 shops and 11,852 independent lab tests across 118 peptides, with 1,283 community reviews (verified August 2026), weighting community reviews and independently verified HPLC purity equally at 50% each, with no financial relationships influencing the ranking — the methodology is documented at how we calculate trust scores.

The number to be careful with is the headline one. A 99.70% average across 242 tests is a genuinely strong result and it is the least informative figure on this compound, because a pure sample of melanotan II returns the same chromatogram. None of that testing volume answers the question a PT-141 buyer most needs answered.

The trial that would settle this is not a testing study either. The vial is verifiable with the right instrument; the use most buyers have in mind is not.

What about compounded PT-141?

Compounded PT-141 has a statutory route on paper, because bremelanotide is a component of an FDA-approved drug — one of the three statutory routes under 21 U.S.C. § 353a(b)(1)(A) for 503A compounding — and it does not appear on FDA's list of bulk substances that may present significant safety risks. As of August 2026 neither fact legitimises a research vial. Selling an approved drug's active ingredient for human use without an application is the sale of an unapproved new drug, and "research use only" labelling is not a defence.

The route being open is an absence rather than a permission. Nothing in that record says FDA has evaluated compounded bremelanotide favourably; it says the statutory prong is satisfied and the substance has not been flagged. Those are different claims, and vendors collapse them routinely. For the structural comparison of what each route carries, see compounding pharmacy versus research peptide.

What the approved route carries that a vial does not is mostly frequency control, and on this compound frequency is a safety variable with a number attached. The approved product is a fixed-dose 1.75 mg / 0.3 mL autoinjector: one dose, one strength, dispensed against a prescription that carries the label's "no more than 8 doses per month" instruction. A reconstituted vial replaces that with whatever concentration your own diluent volume produces, and removes the cap that keeps focal hyperpigmentation at 1% rather than 38%. The peptide dosing calculator and the reconstitution calculator will do that arithmetic; neither restores the prescriber, the cardiovascular screen or the frequency limit.

On cost, we will not complete a comparison we cannot source. This platform's verified figures are research-market figures: a $4.40/mg median, a $2.00/mg low on a 10 mg vial and a $9.59/mg high on a 5 mg vial (verified 10 August 2026). We do not hold a verified pharmacy price for the approved autoinjector, and rather than estimate one to make the comparison symmetrical, we are naming the gap.

Frequently Asked Questions

What purity standard should PT-141 meet?

This platform records PT-141 at 99.70% across 242 independent HPLC tests from Freedom Diagnostics, ILS, Kovera, Accurate Test Lab, MZ Biolabs and Ethos Analytics, across 225 verified shops (verified August 2026). Against a market clearing that high, "above 98%" promises less than the norm. More importantly, purity is the wrong axis on this compound: a 99.70% result would read identically if the vial contained melanotan II.

How much does PT-141 cost?

Price data shows 65 shops in stock at a median of $4.40 per milligram, with the lowest listing at $2.00/mg on a 10 mg vial and the highest at $9.59/mg on a 5 mg vial, across 68 of 77 live listings from 158 known shops (verified 10 August 2026). Vials run 5–10 mg at $20.00–$90.00. Those figures exclude shipping, taxes and customs, coupon codes, bulk tiers, multi-vial kits and account-gated pricing.

Is PT-141 legal, and is it banned in sport?

Bremelanotide is an FDA-approved prescription drug — VYLEESI, NDA 210557, approved 21 June 2019 and currently marketed by Cosette Pharmaceuticals — approved only for acquired, generalised hypoactive sexual desire disorder in premenopausal women. It is not named on the WADA 2026 Prohibited List, and the S0 catch-all turns on having no approval from any governmental health authority, which does not obviously reach an approved drug. An approved drug sold as a research vial for human use is still an unapproved new drug in that form.

How do I know the vial contains PT-141 and not melanotan II?

High-resolution mass spectrometry or MS/MS fragmentation on your batch, confirming 1,025.2 Da rather than 1,024.18. The two peptides share an identical backbone, lactam bridge, D-phenylalanine and norleucine, and differ only in the C-terminal group — an acid against an amide, about 1 dalton on 1,025. HPLC co-elutes them and nominal-mass MS is unreliable at that separation.

How often can PT-141 be dosed, and does frequency matter?

The label allows one 1.75 mg subcutaneous dose at least 45 minutes before anticipated sexual activity, no more than one dose in 24 hours, and states that "more than 8 doses per month is not recommended." Frequency is the variable that controls the most visible adverse effect: focal hyperpigmentation occurred in 1% of patients within that cap and in 38% of patients dosed daily for eight days, with resolution not confirmed in all patients after stopping. No annual cap appears anywhere in the label. For the nasal route some vendors promote, the intranasal peptide guide covers technique, but the approved product is a subcutaneous autoinjector and no intranasal bremelanotide has ever been approved.

Did the trials show PT-141 improves people's sex lives?

The two co-primary endpoints in RECONNECT were questionnaire scores for desire and distress across 1,267 premenopausal women, and both improved by roughly 0.3 points more than placebo, with p-values from 0.0053 to below 0.0001. On satisfying sexual events — the endpoint counting actual encounters — FDA's label states there was "no significant difference between treatment groups." Both findings come from the same regulatory document.

Browse the libido and sexual wellness peptides category, or our complete peptide guide with 118 compounds (verified August 2026). For per-injection volume, use the peptide dosing calculator alongside the reconstitution calculator. Compare shops through independent lab tests and community-verified shop reviews.

This article is for educational and informational purposes only and does not constitute medical advice. Peptides discussed may be investigational compounds not approved by the FDA (or equivalent regulators in your jurisdiction) for human use. Always consult a qualified healthcare provider before using any peptide or research compound. Peptigrity is an independent review platform and does not sell, endorse, or recommend specific products or vendors.