Melanotan II: Reference Overview and Reconstitution Notes

Melanotan II

What it is

Melanotan II is a synthetic cyclic heptapeptide, meaning a ring-shaped chain of seven amino acids closed by an internal lactam bridge. It is a laboratory-made analog of alpha-melanocyte-stimulating hormone (alpha-MSH) and acts as a non-selective agonist at the melanocortin receptors MC1, MC3, MC4, and MC5.

Research context and categorization

Melanotan II is most often grouped under the skin and cosmetic category of research peptides, with additional overlap into neuroendocrine and reproductive signaling because of its receptor activity. It is commonly discussed in relation to melanogenesis, the pigment-production pathway driven through the MC1 receptor, and it has been investigated in early pilot studies for its effect on skin darkening. Because it also activates the MC4 receptor, it is discussed in the context of appetite and neuroendocrine signaling, and it is studied in relation to sexual-function pathways. Notably, arousal-related observations during early Melanotan II research contributed to the separate development of bremelanotide (PT-141), a related compound later approved by the FDA for a specific indication. The uses of Melanotan II itself remain investigational. It has not completed the trials required for approval, and none of the effects described above are confirmed or approved for Melanotan II.

Status

  • Regulatory status: Research-only. Melanotan II is not FDA-approved for any indication and is treated as an investigational, unapproved substance.
  • Sport status: Prohibited under the WADA Prohibited List. As a peptide that lacks regulatory approval for human therapeutic use, it falls under the non-approved substances class (S0), which is banned at all times, both in-competition and out-of-competition.

Reconstitution notes (general)

Lyophilized (freeze-dried) peptides are reconstituted with bacteriostatic water before use in the lab. The resulting concentration equals the milligrams of peptide in the vial divided by the millilitres of bacteriostatic water added. For example, 10 mg reconstituted with 2 mL of bacteriostatic water gives a 5 mg/mL stock. A reconstitution calculator is available at /pages/tools.

Dilution and handling notes (compound-specific)

Melanotan II ships as a lyophilized powder and is one of the more forgiving peptides to reconstitute. A common approach for a 10 mg vial is 2 mL of bacteriostatic water, giving a 5 mg/mL stock; using more water, such as 3 mL to 4 mL, produces a lower, more dilute stock (roughly 3.3 mg/mL or 2.5 mg/mL) that some prefer for finer measurement. Unlike peptides that gel, clump, or resist going into solution when concentrated, Melanotan II typically dissolves quickly and yields a clear, colorless solution within seconds to a minute. Direct the water down the inner glass wall rather than blasting it straight onto the powder cake, then swirl gently rather than shaking or vortexing, since aggressive agitation adds foam and mechanical stress that can promote aggregation. The main compound-specific quirk is light sensitivity: Melanotan II is sensitive to UV and prolonged light exposure, so both the sealed powder and the reconstituted solution should be kept out of light. If the solution turns cloudy, discolored, or shows visible particles, that indicates aggregation, degradation, or contamination, and clarity cannot be restored by further dilution or filtering, so the vial should be discarded.

Handling and storage

Store the reconstituted vial refrigerated at 2 to 8 degrees C and keep it out of direct light at all times, before and after mixing. Wipe the rubber stopper with an alcohol swab before each draw, and label the vial with the mix date so its age can be tracked. A reconstituted solution is generally used within about a four-week refrigerated window. Discard the vial if the contents become cloudy or discolored or develop floaters.

Related reading

Tools and supplies

For laboratory and research reference only. Educational content, not medical, dosing, injection, or therapeutic guidance, and not intended for human or animal use. Any research uses described are investigational and not confirmed or approved benefits. Confirm anything involving health with a licensed professional. References linked above.