PT-141 Reconstitution Calculator, Units & Half-Life
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[Peptide · Compound guide]

PT-141 (Bremelanotide): reconstitution, units and half-life

Vial sizes · Worked example · Units chart · Half-life ~2.7 hours

What is PT-141?

PT-141 (bremelanotide) is a melanocortin receptor agonist. It is FDA approved as Vyleesi, a 1.75 mg autoinjector for premenopausal women with acquired, generalized hypoactive sexual desire disorder (HSDD). The label says it is not indicated for men or to enhance sexual performance.

Also known as: Bremelanotide, Vyleesi.

Common vial sizes

Vyleesi comes in a single-dose autoinjector that needs no mixing. Powder vials of bremelanotide are usually labeled 10 mg.

Water and syringe-unit charts by vial size: 10 mg

Worked reconstitution example

Here is the math for a 10 mg vial mixed with 2 mL of bacteriostatic water, drawing 1.75 mg with a U-100 insulin syringe (1 mL = 100 units).

  1. Concentration. 10 mg ÷ 2 mL = 5 mg/mL
  2. Volume to draw. 1.75 mg ÷ 5 mg/mL = 0.35 mL
  3. Syringe units. 0.35 mL × 100 = 35 units
The amount here is an example to show the math, not a recommendation. How much to take is a decision for you and your prescriber.

Units chart at 5 mg/mL

10 mg vial + 2 mL water. Amounts are examples for the conversion, not doses.
AmountVolumeU-100 syringe
875 mcg0.175 mL17.5 units
1.75 mg0.35 mL35 units
3.5 mg0.7 mL70 units

Same amount, different water volumes

Adding more water doesn't change how much PT-141 is in the vial. It only spreads it over more liquid, so each draw is bigger and easier to read.

1.75 mg from a 10 mg vial.
Water addedConcentrationVolumeU-100 syringe
1 mL10 mg/mL0.175 mL17.5 units
2 mL5 mg/mL0.35 mL35 units
3 mL3.33 mg/mL0.525 mL52.5 units
5 mL2 mg/mL0.875 mL87.5 units

For any other vial size or amount, the free peptide reconstitution calculator works backwards from the amount you want and suggests a water volume that lands on a clean syringe mark.

What does the Vyleesi label say about dosing?

The label dose is 1.75 mg injected under the skin of the abdomen or thigh, as needed, at least 45 minutes before expected sexual activity. It says not to take more than one dose in 24 hours, and more than 8 doses a month is not recommended, because more frequent use raises the risk of darkened skin patches and the time blood pressure is raised.

In the two phase 3 RECONNECT trials (Kingsberg, Obstet Gynecol 2019; 1,267 premenopausal women, 24 weeks), bremelanotide raised desire scores and lowered distress more than placebo. Nausea, flushing and headache each affected 10% or more of women on it.

These are trial protocols, not personalized advice; confirm any dosing with your prescriber.

PT-141 half-life and time to peak

  • Half-lifeabout 2.7 hours
  • Time to peak (Tmax)about 1 hour

The FDA Vyleesi label gives a mean terminal half-life of about 2.7 hours (range 1.9 to 4.0 hours) and a median time to peak of about 1 hour after an injection under the skin, with bioavailability of about 100%.

Numbers shown are taken from the source above. Half-life varies from person to person and with injection site.

How to track PT-141 in Dose Track

  1. Add PT-141 as a custom compound. It is not in the built-in list, but a custom compound gets the same vial, units and reminder tools, and it sits next to everything else you take.
  2. Save your vial: enter the vial size and how much water you added. From then on every amount you log shows as syringe units, and the reconstitution planner suggests a water volume that lands on a clean mark.
  3. Log each shot. The app subtracts it from the vial, shows what is left, and warns you before you run out.
  4. Set reminders on your own schedule, whether that is daily, weekly or every few days.
  5. Your log stays on your phone.
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Frequently asked questions

How much bacteriostatic water do I add to a 10 mg PT-141 vial?+
There is no single right amount. More water makes each draw bigger and easier to measure; less water makes it smaller. For example, 2 mL in a 10 mg vial gives 5 mg/mL, so 1.75 mg is 0.35 mL, or 35 units on a U-100 insulin syringe. That amount is only an example for the math, not a recommendation. The free Dose Track reconstitution calculator works it out for any vial and amount.
How many units is 1.75 mg of PT-141?+
It depends on the concentration in your vial. At 5 mg/mL (10 mg mixed with 2 mL), 1.75 mg is 0.35 mL, which is 35 units on a U-100 insulin syringe, where 1 mL is 100 units. Divide the amount by the concentration to get mL, then multiply by 100.
What is the half-life of PT-141?+
The FDA Vyleesi label gives a mean terminal half-life of about 2.7 hours (range 1.9 to 4.0 hours) and a median time to peak of about 1 hour after an injection under the skin, with bioavailability of about 100%.
Can I track PT-141 in Dose Track?+
Yes, as a custom compound. PT-141 is not in the built-in list, but you can add it yourself. You can then log each shot next to your other compounds, save your vial and how much water you added so every amount shows in syringe units, see how much is left in the vial, and get reminders. Your log stays on your phone.

Sources

  1. Vyleesi (bremelanotide) prescribing information, sections 1, 2 and 12.3. DailyMed, November 2025.
  2. Kingsberg SA, et al. Bremelanotide for the treatment of hypoactive sexual desire disorder: two randomized phase 3 trials. Obstet Gynecol. 2019.

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