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How-to · reconstitution
Put 0.3 mL of bacteriostatic water into the 1.75 mg PT-141 vial. That makes 5.83 mg/mL. A 1.75 mg dose is then 30.0 units on a U-100 syringe.
That volume is the one that lands the draw on a syringe line, so the reading can be checked by eye. More water makes a weaker mix and a bigger draw. Less water makes a stronger mix and a smaller one. The amount of PT-141 in the glass never changes. Only the number of marks it takes does.
PT-141 is the development code for bremelanotide. It acts on melanocortin receptors in the brain, rather than on blood flow the way the erectile-dysfunction pills do.
| Water added | Concentration | Per U-100 unit | Example: 1.75 mg = |
|---|---|---|---|
| 0.3 mL | 5.83 mg/mL | 58.33 mcg | 30.0 units |
Straight arithmetic: concentration = 1.75 mg ÷ water, and 1 U-100 unit = 0.01 mL. The example column shows the math at 1.75 mg; it is not a dose recommendation.
Which volume to use is a practical choice rather than a dose. Pick the one that puts your draw somewhere you can actually read it on the syringe. The flags in the last column mark where that fails. “Hard to measure” means the draw is too small to judge by eye. “Won’t fit” means it is bigger than one U-100 syringe holds.
The table above uses one worked example. These are the published quantities, converted into marks on a U-100 barrel at each water volume for a 1.75 mg vial. Where a quantity was never studied by injection, the row says so.
1.75 mg as needed, at least 45 minutes before sexual activity, under the skin. No more than once in 24 hours and no more than 8 times a month.
| Water added | Concentration | Draw |
|---|---|---|
| 0.3 mL | 5.83 mg/mL | 30.0 units |
FDA labelVYLEESI (bremelanotide) injection — FDA-approved Prescribing Information (DailyMed SPL) · retrieved 2026-08-12
Only one vial strength and one mixing volume are documented, so there is a single calculation to show.
The approved medicine comes in a prefilled autoinjector and requires no mixing. A powder vial is a different preparation and is not described by that label.
The arithmetic still holds for the powder somebody actually bought. It simply has no label behind it, which is a different thing from having a label that disagrees.
Every other guide in this family exists partly to help choose between volumes. With a single listed volume there is nothing to weigh. The concentration settles the moment the powder dissolves.
That leaves only the reading itself, which lands comfortably in the middle of a U-100 barrel.
This is the smallest amount of liquid any preset on the site produces. Whatever clings to the vial wall and sits in the needle hub stays roughly constant. On a fill this small it makes up a larger fraction of the whole.
When the full vial is one dose, residue left behind means receiving slightly less than the full amount. The calculator cannot measure that loss.
The table shows the offered water volumes. The calculator does the same arithmetic for any volume and any syringe, and shows its working line by line.
Open the PT-141 calculator →The arithmetic on this page is only half the question. These are the pages that carry the other half.