PT-141 Reconstitution: Water per Vial, mg/mL and Units

How 5 mg and 10 mg PT-141 vials convert to mg/mL and U-100 units for the 1 mg to 2 mg figures pages state, beside the Vyleesi label's 1.75 mg in 0.3 mL.

Medibact Guides · Published 2026-09-18

Illustration: A partially filled clear glass vial on a white surface, lit by soft natural light. — Illustration

PT-141 is bremelanotide, a seven-amino-acid cyclic peptide that acts on melanocortin receptors and is the active metabolite of Melanotan II. It is the rare compound on this hub with an approved product behind it: VYLEESI, a single-dose subcutaneous autoinjector approved in the United States, whose label states a dose and a concentration. The research market sells the same peptide as a lyophilized powder in 5 mg and 10 mg vials, the sizes the PT-141 calculator is built around, and it is that vial this page is about. It reports the water volumes the sources state, the concentration each produces, and what the milligram figures pages quote come to on a U-100 syringe, beside the label's own figures. It reports and does not recommend. The figures and their provenance are on the PT-141 dosage page; every compound's arithmetic is indexed on the reconstitution hub.

What the sources state

Source	What it states	Kind of source	Opened
VYLEESI (bremelanotide) injection label, DailyMed set id f1d0c1b5-2f39-4bad-a6a4-0066e3ad5dcf	1.75 mg subcutaneously into the abdomen or thigh, at least 45 minutes before anticipated sexual activity; not more than one dose within 24 hours; more than 8 doses per month not recommended; "the duration of efficacy after each dose is unknown"; each autoinjector 1.75 mg in 0.3 mL with 2.5% glycerin and sterile water; store at or below 25 °C, protect from light, do not freeze; indicated for premenopausal women with acquired, generalized HSDD; "not indicated for the treatment of HSDD in postmenopausal women or in men" and "not indicated to enhance sexual performance"	Approved label, revised March 2024, published 2025-11-18	2026-09-18
ClinicalTrials.gov, bremelanotide as intervention	Ten records, including NCT02333071 (Phase 3, completed), NCT04943068 (Phase 3 bridging, completed) and NCT06565611 (Phase 2 with tirzepatide, active)	Trial registry	2026-09-18
PubMed	94 records with bremelanotide in the title or abstract; 11 tagged as clinical trials	Literature database	2026-09-18
Path To Peptides, PT-141 protocol guide	10 mg vial in 2 mL, 5 mg/mL; 1 mg is 20 units, 1.75 mg is 35 units, 2 mg is 40 units; "Starting dose 1mg", "Standard dose 1.75mg", "Max single dose 2mg"; 45 to 60 minutes before; not more than once in 24 hours; not more than 8 doses a month; cites the Vyleesi label dose	Vendor-side protocol page, 2026	2026-09-18

The protocol page's figures are the label's figures, plus a 1 mg floor and a 2 mg ceiling of its own, applied to a vial the label does not describe.

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Water per vial and the concentration it gives

The calculator works both vials at 1, 2 and 3 mL; the protocol page's 10 mg in 2 mL is one of those rows, and the autoinjector's own solution is added for comparison. One U-100 unit is a hundredth of a millilitre (MedlinePlus, "Giving an insulin injection", reviewed 2024-07-21).

Presentation	Water added	Concentration	Micrograms per unit
5 mg vial	1 mL	5 mg/mL	50 mcg
5 mg vial	2 mL	2.5 mg/mL	25 mcg
5 mg vial	3 mL	1.67 mg/mL	16.7 mcg
10 mg vial	1 mL	10 mg/mL	100 mcg
10 mg vial	2 mL	5 mg/mL	50 mcg
10 mg vial	3 mL	3.33 mg/mL	33.3 mcg
Vyleesi autoinjector	none, a solution	5.83 mg/mL (1.75 mg in 0.3 mL)	58.3 mcg

The autoinjector's concentration sits close to the protocol page's 5 mg/mL, which is why the two produce similar-looking draws: 0.3 mL from the device and 0.35 mL from the vial. They are still different products.

The stated milligram amounts in syringe units

The protocol page states 1 mg, 1.75 mg and 2 mg; the label states 1.75 mg only.

Presentation	1 mg	1.75 mg	2 mg
10 mg in 1 mL	10 units	17.5 units	20 units
10 mg in 2 mL, or 5 mg in 1 mL	20 units	35 units	40 units
10 mg in 3 mL	30 units	52.5 units	60 units
5 mg in 2 mL	40 units	70 units	80 units
5 mg in 3 mL	60 units	105 units, more than one barrel	120 units
Vyleesi autoinjector, 5.83 mg/mL	17 units	30 units (0.3 mL, the whole device)	34 units

Two things the table makes visible. The 1.75 mg figure is not a round number of units at any research-vial concentration except 5 mg/mL (35 units) and 10 mg/mL (17.5, a half-unit reading), because it was set for a device that delivers 0.3 mL, not for a syringe; and a 5 mg vial at 3 mL cannot deliver it in one insulin syringe at all. The count per vial is unchanged by any of this: a 10 mg vial holds five 2 mg amounts, or five 1.75 mg amounts with 1.25 mg left over, and a 5 mg vial half as many.

Why the label dose and the vial dose are different claims

The 1.75 mg on the label is a metered quantity delivered by a device from a product whose identity, content and sterility are the manufacturer's legal responsibility, tested for an indication the label names: acquired, generalized hypoactive sexual desire disorder in premenopausal women. The same label rules out, in so many words, use in postmenopausal women, use in men and use to enhance sexual performance, and states that the duration of effect after a dose is unknown.

A vial labelled "PT-141 10 mg" describes what a seller says is in it. Drawing 35 units of a 5 mg/mL solution from it delivers 1.75 mg only if the vial contains 10 mg of the stated peptide and nothing else, an assumption the arithmetic makes and cannot check. The number carried from the label to the vial is real; the authority behind it does not travel with it. That is the point of keeping the two presentations in separate rows above.

The mixing steps, as a label describes them

The Vyleesi label has no reconstitution steps, because its product is a solution. The labelled procedure for a lyophilized peptide supplied with bacteriostatic water is in the EGRIFTA WR (tesamorelin) prescribing information revised in March 2025: only the supplied Bacteriostatic Water for Injection is used; the stated volume is added to the vial; the vial is moved in a circle to mix the powder and liquid and is not shaken; the solution is inspected and not used if particles appear or it is cloudy or coloured. The general procedure for any lyophilized vial, step by step, is on Medibact's how to reconstitute peptides page and is not repeated here.

Storage after mixing

The only label statement is for the autoinjector, which is never mixed: store at or below 25 °C, do not freeze, protect from light; no label covers a reconstituted research vial, and what labels and manufacturers state about reconstituted peptides is on Medibact's how to store peptides page.

What this page does not do

It does not state an amount of PT-141 to use, a timing, a frequency or a limit. The 1.75 mg figure is reported because a label states it, with the label's own indication and its exclusions; the 1 mg and 2 mg figures are reported because a protocol page states them, and that page's authority for them is the same label applied to a different product. The arithmetic converts stated inputs exactly and says nothing about whether any input is appropriate. Medibact's PT-141 guide covers the compound; Peptifact's PT-141 dosage page reads the label's exclusions against the market for the vial. Decisions about administering anything to a person belong with a clinician.

Sources and dates

Opened 2026-09-18: the VYLEESI (bremelanotide) injection label on DailyMed, set id f1d0c1b5-2f39-4bad-a6a4-0066e3ad5dcf (sections 1, 2, 11, 16 and the storage statement; revised 3/2024; published 2025-11-18); the DailyMed SPL search API for "bremelanotide" (one record); the ClinicalTrials.gov v2 API for bremelanotide as an intervention (ten records, NCT02333071, NCT04943068 and NCT06565611 among them); PubMed through the NCBI E-utilities for bremelanotide[tiab] (94 records) and with the clinical-trial and randomized-controlled-trial filters (11); the Path To Peptides PT-141 protocol guide (2026); the EGRIFTA WR prescribing information (revised 3/2025, section 2.2); MedlinePlus, "Giving an insulin injection" (reviewed 2024-07-21). Corrections go to the contact page.

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Medibact Guides facts

PT-141 is bremelanotide, a melanocortin-receptor agonist and the active metabolite of Melanotan II. Unlike most compounds on this hub it is an approved medicine: VYLEESI, a single-dose subcutaneous autoinjector (Cosette Pharmaceuticals; label revised March 2024, published on DailyMed 2025-11-18, opened 2026-09-18).
The Vyleesi label's dose is 1.75 mg injected subcutaneously into the abdomen or thigh at least 45 minutes before anticipated sexual activity; the label states that no more than one dose is administered within 24 hours, that more than 8 doses per month is not recommended, and that 'the duration of efficacy after each dose is unknown'.
The approved indication is acquired, generalized hypoactive sexual desire disorder in premenopausal women; the label's Limitations of Use state that Vyleesi 'is not indicated for the treatment of HSDD in postmenopausal women or in men' and 'is not indicated to enhance sexual performance'.
Each autoinjector contains 1.75 mg of bremelanotide in 0.3 mL of solution, which is 5.83 mg/mL, with 2.5% glycerin and sterile water for injection. It is a solution that is never reconstituted, stored at or below 25 °C, protected from light and not frozen.
Research vials are 5 mg and 10 mg of lyophilized powder, the sizes the calculator carries. A protocol page opened on 2026-09-18 works a 10 mg vial in 2 mL of bacteriostatic water, 5 mg/mL, so that 1 mg is 20 units, 1.75 mg is 35 units and 2 mg is 40 units on a U-100 syringe; it states 1 mg as a starting figure, 1.75 mg as standard and 2 mg as a maximum, and repeats the label's 45-minute, once-in-24-hours and eight-per-month limits (Path To Peptides, 2026).
At the calculator's water volumes a 10 mg vial gives 10, 5 and 3.33 mg/mL in 1, 2 and 3 mL, so 1.75 mg is 17.5, 35 and 52.5 units; a 5 mg vial gives 5, 2.5 and 1.67 mg/mL, so the same amount is 35, 70 and 105 units, the last of which exceeds a 1 mL syringe.
Bremelanotide has more human evidence than anything else on this hub: PubMed held 94 records on 2026-09-18, 11 tagged as clinical trials, and ClinicalTrials.gov ten registrations, including the completed Phase 3 trial NCT02333071 in premenopausal women and an active Phase 2 study of bremelanotide co-administered with tirzepatide (NCT06565611).
The label figure and a research-vial figure are not the same claim: 1.75 mg from the autoinjector is a metered dose of a product with a label, a lot number and a manufacturer; 1.75 mg drawn from a vial labelled 10 mg is 35 units of whatever the vial actually contains, at a concentration set by the water added.
A 10 mg vial holds five 2 mg amounts, or five 1.75 mg amounts with 1.25 mg left over, at any water volume, and a 5 mg vial half as many; the water changes the draw, not the count.

Frequently asked questions

How much water goes into a 10 mg vial of PT-141?

No label sets it, because the labelled product is a ready-made autoinjector and the research vial has no label. The protocol page opened on 2026-09-18 works a 10 mg vial at 2 mL of bacteriostatic water, 5 mg/mL. The calculator's columns give 10 mg/mL at 1 mL, 5 mg/mL at 2 mL and 3.33 mg/mL at 3 mL, and half of each for a 5 mg vial. The volume sets how many units a milligram occupies; the mass in the vial does not change.

How many units is 1.75 mg of PT-141 on an insulin syringe?

At 5 mg/mL, the protocol page's 10 mg in 2 mL, 35 units. At 10 mg/mL (10 mg in 1 mL) 17.5 units; at 3.33 mg/mL (10 mg in 3 mL) 52.5 units; at 2.5 mg/mL (5 mg in 2 mL) 70 units; at 1.67 mg/mL (5 mg in 3 mL) 105 units, which no longer fits a 1 mL syringe. The autoinjector delivers the same 1.75 mg in 0.3 mL, which would read as 30 units at its 5.83 mg/mL. The figure only means something next to the concentration.

What is the approved PT-141 dose?

The Vyleesi label states 1.75 mg injected subcutaneously into the abdomen or thigh, as needed, at least 45 minutes before anticipated sexual activity, with no more than one dose within 24 hours; more than 8 doses per month is not recommended. The label adds that the duration of efficacy after each dose is unknown. It is a fixed dose from a single-use autoinjector, for premenopausal women with hypoactive sexual desire disorder, and nothing on the label is a titration, a loading phase or a cycle.

Does the Vyleesi label cover a reconstituted research vial?

No. The label describes a 0.3 mL solution in a prefilled autoinjector, never a powder or a diluent volume, and its Limitations of Use state that the product is not indicated for postmenopausal women or men and not indicated to enhance sexual performance, which is most of what research vials are marketed for. A page quoting 1.75 mg for a 10 mg vial is borrowing a figure from a document written for a different product, a different population and a stated purpose the document rules out.

How much evidence is behind the 1.75 mg figure?

More than for any other compound on this hub. Bremelanotide had 94 PubMed records on 2026-09-18, 11 of them tagged as clinical trials, and ten registrations on ClinicalTrials.gov, including the completed Phase 3 study NCT02333071 in premenopausal women and a bridging Phase 3 study. A Phase 2 study of bremelanotide co-administered with tirzepatide (NCT06565611) was active when checked. All of it concerns the autoinjector or its predecessors, and none of it a reconstituted vial.

How is PT-141 reconstituted?

The research vial is a lyophilized powder with no label, so the procedure is the one labels describe for lyophilized peptides supplied with bacteriostatic water: the EGRIFTA WR label, revised March 2025, has the stated volume of diluent added, the vial moved in a circle to mix rather than shaken, and the solution inspected and used only if clear and free of particles. The Vyleesi label contains no such steps because its product is already a solution. Medibact's reconstitution page carries the general procedure.