What this does
Divide milligrams in the vial by millilitres of water for concentration, then the dose by that for the draw, then multiply by 100 for U-100 units. A 10 mg vial in 2 mL is 5 mg/mL, so the 1.75 mg on the approved Vyleesi label is a 0.35 mL draw, or 35 units.
The vial size above is the size this compound is most commonly sold in, not a specification. Change it to match your label. The dose stays whatever you set — this tool does not suggest one.
What size vial does PT-141 come in?
Research vials are most often 10 mg. The approved pharmaceutical, Vyleesi, is not a vial at all — it is a single-use autoinjector, which is part of why the two are not interchangeable in any practical sense.
The same 10 mg vial at four water volumes:
| Water added | Concentration | Units for a 1 mg draw |
|---|---|---|
| 1 mL | 10 mg/mL | 10.0 units |
| 2 mL | 5 mg/mL | 20.0 units |
| 3 mL | 3.33333 mg/mL | 30.0 units |
| 5 mL | 2 mg/mL | 50.0 units |
Each row holds the same 10 mg. Water sets how large the draw is, not how many draws the vial contains.
What is the approved dose?
Bremelanotide, marketed as Vyleesi, is approved at 1.75 mg subcutaneously, as needed, for hypoactive sexual desire disorder in premenopausal women. That figure comes from a licensed label rather than from this site.
Two things it does not mean. It is not an endorsement of a research vial, which is a different product with different manufacturing behind it. And the licensed indication is narrow — the trials that produced it enrolled premenopausal women, which is not most of the search traffic for this compound. The PT-141 dosage page covers the trial protocols and the HSDD research covers what they measured.
Worth knowing before running any number: the approved label carries a transient blood-pressure rise and a nausea rate high enough to matter. The PT-141 guide sets that out.
The trap on this one: the nasal route is not this arithmetic
PT-141 is widely sold as a nasal spray, and the calculator above does not describe it. A nasal formulation has its own bioavailability, and milligrams into a nostril are not milligrams under the skin.
The development history is the reason this matters. An intranasal formulation was taken forward and then abandoned; the approved product is subcutaneous. Converting a subcutaneous figure into a nasal volume is not a calculation anyone can do from the numbers on the vial.
The PT-141 nasal spray page covers what happened to that route and why the two are not convertible.
Frequently asked questions
How many units is 1.75 mg of PT-141?
At 10 mg in 2 mL, which is 5 mg/mL, 1.75 mg is 0.35 mL — 35 units on a U-100 insulin syringe. Change the water volume and the unit figure changes with it.
What is the approved PT-141 dose?
Bremelanotide is approved as Vyleesi at 1.75 mg subcutaneously, as needed, for hypoactive sexual desire disorder in premenopausal women. That is a licensed label figure for a specific product and indication, not a recommendation for a research vial.
Can I use this calculator for PT-141 nasal spray?
No. The arithmetic here converts milligrams into a subcutaneous draw volume. A nasal formulation has different bioavailability, and there is no way to convert between the two from the numbers on a vial.
How much water should I add to a PT-141 vial?
Your choice. 2 mL of bacteriostatic water in a 10 mg vial gives 5 mg/mL. More water makes each draw larger and easier to measure; the vial still holds 10 mg either way.
References
- American Society of Health-System Pharmacists (ASHP). Handbook on Injectable Drugs: Benzyl alcohol preservative compatibility and stability data. https://www.ashp.org/products-and-services/database-tools/handbook-on-injectable-drugs
- United States Pharmacopeia. (2024). Bacteriostatic Water for Injection — monograph and in-use stability guidance. USP-NF. (See institutional access.) https://doi.org/10.4135/9781412963855.n1200
- Wang, W. (1999). Instability, stabilization, and formulation of liquid protein pharmaceuticals. International Journal of Pharmaceutics, 185(2), 129–188. https://doi.org/10.1016/s0378-5173(99)00152-0
The arithmetic needs no citation; the diluent and stability guidance does.