How to Use This Calculator
Pick your vial size (5 or 10 mg, or type a custom amount), then enter how much bacteriostatic water you added, the dose in mg and your syringe size. Click Calculate to see how many units and mL to draw, the concentration in mg/mL and how many full doses the vial holds. If the draw is too big for the syringe you chose, the calculator tells you.
What Is PT-141?
PT-141 is the research name for bremelanotide, a short, ring-shaped peptide of seven amino acids that was developed from melanotan II. It works on melanocortin receptors in the brain, mainly the MC4 receptor, which is linked to sexual desire, rather than on blood flow.
The Approved Product: Vyleesi
The FDA approved bremelanotide as Vyleesi on June 21, 2019. Vyleesi is a prefilled autoinjector that gives 1.75 mg in 0.3 mL under the skin of the belly or thigh. Its label says to inject at least 45 minutes before expected sexual activity, to use no more than one dose in 24 hours and to use no more than 8 doses a month. These label details are shown as context, not as a dose to follow. (Source: Vyleesi prescribing information.)
Choosing the Water Volume and Syringe
More water means a weaker solution, so each dose becomes a bigger draw that is easier to measure but may not fit a 0.3 mL or 0.5 mL syringe. The BAC Water Calculator helps you pick a water volume that gives a clean draw, and the Syringe Volume Calculator shows where that draw sits on each barrel size. To see how long your supply lasts and what it costs, use the Peptide Vial Yield Calculator and the Peptide Cycle Cost Estimator.
Who Should Use This
Researchers working with lyophilised PT-141 who need to reconstitute a vial and turn a dose in mg into syringe units.
What This Calculator Does
The PT-141 Dosage Calculator turns a vial size, the bacteriostatic water added and a dose in mg into the draw on a U-100 insulin syringe. It shows the units and mL to draw, the concentration and how many full doses the vial holds.
Formula Used
Concentration (mg/mL) = Vial size (mg) / BAC water (mL)Volume per dose (mL) = Dose (mg) / ConcentrationUnits to draw = Volume (mL) x 100 (U-100 syringe)Doses per vial = FLOOR(Vial size / Dose)Example Calculation
Limitations
This is a unit-conversion tool, not dosing guidance. It assumes the whole vial dissolves and a U-100 syringe, and it ignores dead space and draw loss. Vyleesi comes ready to inject, so this calculator does not apply to it.
Frequently Asked Questions
Is PT-141 FDA-approved?
Bremelanotide was approved on June 21, 2019 as Vyleesi, for premenopausal women with acquired, generalized hypoactive sexual desire disorder. Vyleesi is a ready-to-use 1.75 mg autoinjector. PT-141 sold in research vials is not an approved product.
How many units is 1.75 mg of PT-141?
It depends on the water in the vial. With 10 mg in 1 mL, 1.75 mg is 17.5 units. With 10 mg in 2 mL, it is 35 units, which will not fit a 30-unit syringe. With 10 mg in 3 mL, it is 52.5 units. All three are on a U-100 syringe.
How many doses are in a 10 mg vial of PT-141?
Divide 10 by the dose and round down. At 1 mg you get 10 doses. At 1.75 mg you get 5 full doses, with 1.25 mg left over.
How often does the Vyleesi label allow a dose?
The Vyleesi label says no more than one dose in 24 hours and no more than 8 doses a month, taken at least 45 minutes before expected sexual activity. That applies to the approved product, and this site does not give dosing advice.
Does the syringe size change the number of units?
No. On any U-100 syringe, units are always mL x 100, so 0.2 mL is 20 units on a 1 mL, 0.5 mL or 0.3 mL barrel. A smaller syringe only changes how much it can hold.