PT-141 (Bremelanotide): Reference Overview and Reconstitution Notes

PT-141 (bremelanotide) is a man-made peptide (a small chain of amino acids) that activates certain receptors in the brain. It is grouped with reproductive and sexual-health research compounds, and it has one specific FDA-approved use.

PT-141 (Bremelanotide)

What it is

PT-141, also called bremelanotide, is a man-made cyclic heptapeptide (a small, ring-shaped chain of seven amino acids). It works as a melanocortin receptor agonist, meaning it binds to and switches on specific receptor proteins in the brain called MC3R and MC4R. Think of it like a key shaped to fit two particular locks in the brain. It belongs to the melanocyte-stimulating hormone family of compounds and was built from an earlier compound in that same family.

Key point: PT-141 is FDA-approved under the brand name Vyleesi. It is approved specifically for treating acquired, generalized hypoactive sexual desire disorder (HSDD), a recognized condition involving low sexual desire, in women who have not yet reached menopause.

Research context and categorization

PT-141 is grouped as a reproductive and sexual-health compound. More broadly, it belongs to the melanocortin receptor agonist family. Most research discussion focuses on how it relates to central pathways for sexual arousal and desire. "Central" here means the activity happens in the brain, not in blood vessels.

This brain-based mechanism is different from approaches that work by widening blood vessels. That difference is the basis for its one approved use. Outside that approved use, PT-141 is sometimes discussed in relation to broader questions of arousal and desire across different populations. Those wider uses remain investigational, meaning they have not been confirmed or approved.

Status

• Regulatory status: FDA-approved for a specific use. Bremelanotide is approved under the brand name Vyleesi for acquired, generalized hypoactive sexual desire disorder (HSDD) in premenopausal women. Any use outside that specific indication is off-label or investigational.
• Sport status: Not specifically listed on the WADA (World Anti-Doping Agency) Prohibited List. As of the current List, bremelanotide is not named under any prohibited class. Because it is an FDA-approved substance, it does not automatically fall under the S0 category (which covers substances with no approval at all). Status can change with WADA's annual review, so competitive athletes should check the current List directly.

Reconstitution notes (general)

PT-141 is supplied as a lyophilized (freeze-dried) powder. Freeze-drying removes all water from the compound, much like how instant coffee is made. Before lab use, the powder is mixed back with bacteriostatic water (sterile water with a small amount of preservative added to slow microbial growth). The resulting concentration equals the milligrams of peptide in the vial divided by the millilitres of water added.

For example, a 10 mg vial mixed with 2 mL of bacteriostatic water gives a concentration of 5 mg/mL. To calculate the concentration for any vial size and water volume, use the calculator at peptide calculator.

Dilution and handling notes (compound-specific)

Reconstitution Ratios

PT-141 research vials most often come in 5 mg or 10 mg sizes. A 10 mg vial is commonly mixed with roughly 1 mL to 3 mL of bacteriostatic water. Using 2 mL is a popular choice because it produces a clean 5 mg/mL concentration that is easy to measure on a standard insulin syringe.

Using more water lowers the concentration and makes small measured amounts easier to read on the syringe. Using less water raises the concentration. The amount of water is chosen mainly to reach a convenient working concentration, not because of how well the powder dissolves.

Best Practices for Reconstitution

PT-141 is one of the more cooperative peptides to work with in the lab. It is small and water-friendly, so it usually dissolves quickly into a clear, colourless solution. It does not tend to gel, clump, or resist dissolving the way some larger peptides can.

Good technique still matters to prevent handling problems. Follow these steps during the mixing process:

1. Let the vial reach room temperature before opening.
2. Direct the bacteriostatic water slowly down the inner glass wall of the vial rather than spraying it straight onto the powder.
3. Swirl the vial gently or turn it slowly upside down. Do not shake or vortex it, because rough mixing can cause foaming and lead to aggregation (where molecules clump together into larger, inactive clusters).

If the finished solution turns cloudy, develops colour, or shows floating particles, that points to aggregation, degradation (breakdown of the compound), or contamination. Adding more water or filtering cannot fix this. The vial should be discarded rather than used.

A nasal-spray research format also exists for this compound. That format is a ready-made liquid and does not involve the powder reconstitution steps described above.

Handling and storage

• Refrigerate at 2 to 8 degrees Celsius.
• Keep out of light, both before and after reconstitution.
• Wipe the rubber stopper with an alcohol swab before each puncture.
• Label the vial with the mix date so you can track how old the solution is.
• Follow the general roughly 4-week refrigerated window for the reconstituted solution.
• Discard anything cloudy, discoloured, or containing floating particles.

Related reading

• How Reconstitution Works
• How Long Does a Reconstituted Vial Last?
• Storage Guide

Tools and supplies

• peptide calculator
• Bacteriostatic Water 30 ml
• Gansulin Metal Reusable Pen
• 3 ml Glass Cartridges (10-pack)
• Complete Starter Kit

Reminder: research and educational reference only. Preppin Peppers sells hardware and materials, not peptides. Not medical, dosing, or health advice, not evaluated by the FDA, and not intended for human or animal use.

Frequently asked questions

What receptors does PT-141 (bremelanotide) bind to?

PT-141 is a melanocortin receptor agonist that binds MC3R and MC4R, receptor proteins in the brain linked to central pathways studied in arousal and desire research.

Is bremelanotide FDA approved?

Yes. Bremelanotide is FDA-approved as Vyleesi for acquired, generalized hypoactive sexual desire disorder (HSDD) in premenopausal women. All other uses are off-label or investigational.

How do you reconstitute PT-141 lyophilized powder for research?

Add bacteriostatic water to the vial and divide the vial's milligrams by the milliliters of water added to get concentration in mg/mL. Example: 10 mg + 2 mL = 5 mg/mL.

What the research community gets wrong about PT-141 (Bremelanotide)

• Thinking it acts like a blood-vessel compound. PT-141 is a melanocortin receptor agonist that binds MC3R and MC4R, receptor proteins in the brain. It does not work the way vessel-widening compounds do. When you label vials or file notes at the bench, group it with central (brain-pathway) melanocortin compounds, not with vascular ones.
• Assuming every use is approved. Only one specific human use is FDA-approved (as Vyleesi). Everything else studied in the literature is investigational, meaning it has not been confirmed or approved. Keep that distinction clear in any reference sheet you keep for a study.
• Over-worrying about it clumping. PT-141 is a small cyclic heptapeptide (a ring-shaped chain of seven amino acids) and is water-friendly, so it usually goes into a clear, colourless solution fast. It does not resist dissolving the way some larger peptides do. Reaching for extra force or heat to make it dissolve is not needed and can cause problems.
• Shaking the vial to speed things up. Rough mixing adds air and shear that can cause foaming and aggregation (molecules clumping into larger, inactive clusters). Swirl gently or invert slowly instead. If a solution turns cloudy, gains colour, or shows floating bits, filtering or adding water will not fix it, and the vial should be discarded.
• Mixing up the two formats. A nasal-spray research format is a ready-made liquid, so it skips the powder reconstitution steps entirely. Confirm which format is on your bench before you plan a mixing volume, because the powder math (milligrams divided by millilitres) only applies to the lyophilized vial.

From our bench: If you reconstitute a PT-141 vial, we would like your real handling data. Note the vial size in milligrams, the exact volume of bacteriostatic water you add, and the time from adding water to a fully clear solution when you only swirl (no shaking). Then check the vial again at the end of your refrigerated storage window and record whether any cloudiness, colour, or floating particles appear. Send us your numbers so we can compare notes across different vial sizes.

Sources

1. Bacteriostatic Water for Injection, USP , FDA/DailyMed label (0.9% benzyl alcohol)
2. Duerkop et al., Biotechnol J 2018 , Impact of Cavitation, High Shear Stress and Air/Liquid Interfaces on Protein Aggregation
3. Sigma-Aldrich (Merck) , Handling and Storage Guidelines for Peptides and Proteins
4. PubChem: Bremelanotide (CID 9941379), National Library of Medicine
5. DailyMed: VYLEESI (bremelanotide) injection label, FDA/NLM
6. Kingsberg et al., Bremelanotide for Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials, Obstet Gynecol 2019 (PubMed 31599840)