PT-141 (Bremelanotide) Dosage Guide: Units, Timing and Reconstitution

PT-141, also called bremelanotide, is a melanocortin-receptor peptide studied in clinical and research settings. It ships as a freeze-dried (lyophilized) powder, commonly in a 10 mg vial, and has to be reconstituted with bacteriostatic water before any volume can be measured. This guide covers the arithmetic and the general reference points around PT-141 dosage: how vial strength and diluent volume set the concentration, how a milligram figure converts into units on an insulin syringe, and the timing and monthly-cap numbers that appear in the literature.

Everything here is third-person reference information for research and educational use. It is not dosing advice, and PT-141 is not approved for human consumption. Any decision about whether or how much to use belongs with a licensed clinician. To run your own numbers instead of the worked examples below, use the peptide dosage calculator.

The three numbers that drive the math

Reconstitution reduces to one concentration value and two conversions. You need the vial strength in milligrams, the volume of bacteriostatic water you add in milliliters, and the dose you want to express, in milligrams.

• Concentration = vial strength / water volume. A 10 mg vial in 2 mL gives 5 mg/mL.
• Draw volume = dose / concentration. A 1.75 mg figure at 5 mg/mL is 0.35 mL.
• Units = draw volume x 100 on a U-100 insulin syringe. 0.35 mL reads as 35 units.

Reconstituting a 10 mg vial at 5 mg/mL

A 10 mg vial with 2 mL of bacteriostatic water is the common reference setup for PT-141 because it lands on round, easy-to-read units across the typical milligram range. That mix gives 5 mg/mL. At this concentration the figures most often discussed in the literature convert cleanly.

• 1.5 mg = 0.30 mL = 30 units
• 1.75 mg = 0.35 mL = 35 units
• 2 mg = 0.40 mL = 40 units

At 5 mg/mL a 10 mg vial holds about 5 reference doses of 2 mg, or roughly 5.7 at 1.75 mg. If you want smaller numbers on the barrel, adding more water lowers the concentration and raises the unit count for the same milligram figure. Aim the water down the vial wall and swirl rather than shake, the same as in any peptide reconstitution routine.

The 1.75 to 2 mg reference range

Across protocols described in the research literature, PT-141 figures are commonly discussed in a 1.75 to 2 mg range per administration. The table below shows how that range maps to units at two standard concentrations. These are arithmetic conversions, not recommendations.

• 1.75 mg: 35 units at 5 mg/mL, 17.5 units at 10 mg/mL
• 2 mg: 40 units at 5 mg/mL, 20 units at 10 mg/mL

To reach 10 mg/mL, reconstitute the same 10 mg vial with 1 mL of water instead of 2 mL. Every milligram figure then draws to half the volume and half the units. The tradeoff is a smaller total liquid volume and tighter marks to read on the syringe. The mg to units converter isolates this final mass-to-units step if you change either input.

Timing and the monthly cap

Two non-arithmetic numbers appear repeatedly in PT-141 reference material. The first is timing: clinical labeling describes administration roughly 45 minutes ahead of anticipated activity, since the peptide is not instantaneous. The second is frequency. Published labeling describes a limit of one dose in any 24-hour window and no more than 8 doses per month.

• Reference timing: about 45 minutes before anticipated activity
• Spacing: at most one administration per 24 hours
• Monthly cap: no more than 8 administrations in a month

Storage and recompute notes

General references describe reconstituted peptides as kept refrigerated and used within roughly a few weeks. Bacteriostatic water (saline with benzyl alcohol) is the usual diluent for multi-draw vials because the preservative limits microbial growth between draws. If you change the vial size, the water volume, or the target milligram figure, recompute from scratch rather than reusing an old unit count. The reconstitution calculator handles the same math for PT-141 and other research peptides.