The study shows that injecting melanotan‑I under the skin (subcutaneously) works well for tanning, while taking it by mouth does nothing. A dose of about 0.16 mg per kg given in ten injections over two weeks produces noticeable skin darkening that can last for weeks, with only mild stomach upset or facial flushing as side effects.

A comparative pharmacokinetic trial was performed with a superpotent synthetic melanotropic peptide, [Nle4-D-Phe7]-alpha-MSHi-13 (melanotan-I or MT-I) given by three routes of administration. Plasma levels were measured by RIA and tanning was quantiated using serial reflectometry. Doses of 0.16 mgkg-1 were administered intravenously (IV) and orally (PO), and doses from 0.08 to 0.21 mg kg-1 subcutaneously (SC), in a randomized crossover fashion to three male volunteers over five consecutive days for 2 weeks (ten doses). The results indicate that the SC dose is completely bioavailable compared to the IV dose. No detectable drug levels were observed following PO dosing. The plasma half-lives following SC dosing ranged from 0.07 to 0.79 h for the absorption phase and from 0.8 to 1.7 h for the beta-phase. Clearance ranged from 0.12 to 0.19 L kg-1 h-1 and 3.9% or less of the dose was recovered in the urine. Side-effects were minimal, consisting of occasional gastrointestinal upset and facial flushing. Significant tanning of the forehead, arms, and neck was noted following IV or SC dosing. This effect peaked at 1 week following drug administration but was still present 3 weeks after completing the ten-dose regimen. It is concluded that SC administration is an efficacious method of delivering melanotan-I.