PT-141 Reconstitution Calculator (mg → units)
A 10 mg vial of PT-141 mixed with 2 mL of bacteriostatic water holds 5,000 mcg/mL, so a 1.75 mg dose is 0.35 mL — 35 units on a U-100 insulin syringe. Change the vial, water or dose below, or read the chart for other mixes.
PT-141 dilution chart: 1.75 mg in units
| Vial | + 1 mL water | + 2 mL water | + 3 mL water | Doses per vial |
|---|---|---|---|---|
| 5 mg | 35 U 0.35 mL · 5,000 mcg/mL | 70 U 0.7 mL · 2,500 mcg/mL | 105 U 1.05 mL · 1,667 mcg/mL over 1 mL — more than one syringe | 2.9 |
| 10 mg | 17.5 U 0.175 mL · 10,000 mcg/mL | 35 U 0.35 mL · 5,000 mcg/mL | 52.5 U 0.525 mL · 3,333 mcg/mL | 5.7 |
1 mL = 100 units on a U-100 syringe. Water volume changes the units per dose, never the number of doses in the vial.
Measuring PT-141: the math that matters
PT-141 is the research name for bremelanotide, and the one approved product, Vyleesi, delivers a fixed 1.75 mg from a single-dose autoinjector with nothing to mix. Reconstitution math only applies to research vials of powder. With a 10 mg vial and 2 mL of bacteriostatic water the solution is 5,000 mcg/mL, so 1.75 mg is 0.35 mL, or 35 units on a U-100 insulin syringe.
The awkward part is that 1.75 does not divide evenly into common vial sizes. A 10 mg vial gives 5.7 portions of 1.75 mg, and a 5 mg vial gives 2.9, so there is always a remainder in the vial that is less than one full amount. Tracking what is left matters more here than with compounds dosed in round numbers: the last draw from a vial will come up short, and topping it up from a new vial means mixing two concentrations in one syringe calculation.
The decimal is also where typing errors creep in. 1.75 mg is 1,750 mcg. Enter 1.75 with mcg selected and the result is 0.035 units instead of 35; enter 175 with mg selected and it is 3,500 units. If a result looks absurd, the unit switch is usually the reason.
Water volume shifts the draw across a wide range. At 10 mg with 1 mL, 1.75 mg is 17.5 units, which falls between the 2-unit lines of a 1 mL syringe; with 3 mL it is 52.5 units. A 5 mg vial with 3 mL pushes it to 105 units, just over one syringe. Choose the volume that lands the draw on or near a line you can read.
Common PT-141 measuring mistakes
- Typing 1.75 with the unit set to mcg, or 1750 with mg.
- Expecting a whole number of doses from the vial. At 1.75 mg a 10 mg vial runs out after five full draws with a partial one left.
- Using Vyleesi's autoinjector volume as a guide for a reconstituted vial; the concentrations are unrelated.
- Rounding 17.5 units without checking the effect: up to 18 adds about 3%, down to 16 removes about 9%.
- Mixing a 5 mg vial with 3 mL and getting a single dose larger than the syringe.