What PT-141 is
PT-141 (bremelanotide) is a melanocortin receptor agonist, FDA approved as Vyleesi for hypoactive sexual desire disorder in premenopausal women. It acts centrally rather than vascularly, which distinguishes it from the PDE5 inhibitors. Gray-market use spans both sexes at 0.5 to 2 mg as needed.
What we do not know
- The FDA approval is narrow: acquired, generalized hypoactive sexual desire disorder in premenopausal women. Use in men or postmenopausal women is outside what the pivotal trials studied.
- An earlier intranasal formulation was developed for erectile dysfunction and discontinued after blood pressure increases. The transient pressor effect is a known property, not a rumor.
- Hyperpigmentation with repeated dosing is documented; how it behaves over years of off-label use is unstudied.
Reconstitution math
Concentration is everything: the same 5 mg vial gives a different draw for every amount of bacteriostatic water you add. The table uses the common 2 mL setup for each vial size, which puts every unit on a U-100 insulin syringe at 25 mcg for the default vial. Dashes mark draws too small to measure or larger than the syringe.
| Vial | BAC water | Concentration | 0.5 mg | 1 mg | 1.75 mg | 2 mg |
|---|---|---|---|---|---|---|
| 5 mg | 2 mL | 2.5 mg/mL | 20 u | 40 u | 70 u | 80 u |
| 10 mg | 2 mL | 5 mg/mL | 10 u | 20 u | 35 u | 40 u |
Dosing and protocol
Vyleesi label dose is 1.75 mg subcutaneously as needed; research use spans 0.5 to 2 mg.
The label dose is 1.75 mg subcutaneously at least 45 minutes before anticipated activity, with a maximum of one dose per 24 hours and eight per month. Nausea is the dominant side effect and is dose-dependent, which is why community use often starts at 0.5 to 1 mg. It is an as-needed compound: no titration schedule, no accumulation.
Pharmacokinetics
PT-141 has published human pharmacokinetics: peak about one hour after a subcutaneous dose; half-life about 2.7 hours. The curves below are normalized one-compartment models built from the cited half-life, the same math the Planner uses. They show shape and timing, not absolute blood levels.
How it is thought to work
Bremelanotide is a melanocortin receptor agonist acting centrally at MC3R and MC4R on the brain pathways involved in sexual desire. This is a different mechanism from PDE5 inhibitors, which act on vascular smooth muscle: it targets desire rather than blood flow.
What the evidence supports
This table grades how well each outcome has been studied in humans, not how well PT-141 works. A strong grade means the question was asked properly, and the answer may still have been negative. Nothing here is inherited from a drug class, a close analog, or the parent molecule of a fragment.
| Outcome | Strongest published evidence |
|---|---|
| Erectile function | Human RCT |
| Hypoactive sexual desire disorder in premenopausal women | Human RCT |
| Transient blood pressure increase | Human RCT |
| Use in men, long term | No data |
Storage and handling
Lyophilized vials keep best cold, dark, and dry; refrigeration is the community default and freezing lyophilized powder is common for long holds. After reconstitution, refrigerate at 2 to 8 C, do not freeze the solution, and date the vial. Bacteriostatic water's preservative keeps multi-dose use practical for about 28 days by USP convention, though our 120-day stability study found the preservative itself outlasts that window.
Got a certificate of analysis with your vial? Run it through our COA Reader: it reads the report in plain English, checks purity and mass against the label claim, and links the testing lab’s own verification page. Our guide to reading a COA explains what the numbers do and do not tell you.
Sources
- Vyleesi prescribing information (Palatin / AMAG, 2019)Prescribing information
- Clayton et al., Bremelanotide for HSDD (RECONNECT), Obstet Gynecol 2019