Melanotan II half-life & pharmacokinetics

Reported half-life

Approximately 2-3 hours plasma half-life after subcutaneous administration. Pigmentation effects (via melanogenesis induction) develop over days-to-weeks of repeated dosing and persist for weeks after discontinuation as melanin turns over. Acute sexual-function effects, when they occur, emerge within 1-2 hours of administration and persist for 4-6 hours.

The half-life and pharmacokinetic profile of Melanotan II reported above is drawn from the published pre-clinical literature. Plasma half-life describes the time taken for the circulating concentration to fall by half after a single dose; tissue half-life — which may be longer for peptides retained in specific organs or matrices — is a distinct and often more relevant parameter for healing research, where the duration of exposure at the injury site matters more than the systemic exposure profile.

Routes of administration studied

• Subcutaneous injection (research and grey-market cosmetic standard route)
• Intranasal (grey-market variant; less consistent PK)

Different routes produce materially different pharmacokinetic profiles for the same peptide. Subcutaneous administration generally produces flatter, more sustained plasma profiles than intravenous bolus dosing; intraperitoneal administration (common in rodent models) is not directly translatable to human routes; oral administration faces the additional challenge of luminal and brush-border peptidase degradation, which is why most research peptides have very low oral bioavailability without protective formulation.

Drug class

Cyclic heptapeptide non-selective melanocortin-receptor agonist (MC1R, MC3R, MC4R, MC5R); synthetic α-MSH analogue with pigmentation and sexual-function effects; not licensed in any jurisdiction.

Mechanism context

Half-life interpretation depends on the underlying mechanism. Melanotan II acts as follows:

Melanotan II (MT-II, Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2) is a cyclic heptapeptide synthesised by systematic medicinal-chemistry optimisation of the α-melanocyte-stimulating hormone (α-MSH) sequence at the University of Arizona in the 1980s (Al-Obeidi, Hadley, Hruby, and colleagues). The molecular design cyclised the α-MSH backbone through an Asp-Lys amide bridge to increase potency and metabolic stability, with additional substitutions (N-terminal acetylation with norleucine at position 1 instead of native methionine, D-phenylalanine at position 4 instead of native L-phenylalanine) to further optimise binding affinity and protease resistance. The result is a compound approximately 1000-fold more potent than native α-MSH on melanogenic endpoints while retaining broad melanocortin-receptor activity.

See the full Melanotan II research profile for the complete mechanism summary, history, study citations, and references.

Practical considerations

Short plasma half-life does not necessarily mean short duration of biological effect. Many peptides — including BPC-157, GHK-Cu, and the thymosin-derived compounds — exhibit tissue retention or mechanistic effects (gene expression, signalling cascades) that outlast plasma exposure by hours to days. The pharmacological half-life and the biological-effect half-life are distinct parameters that must both be specified in any rigorous research design. Repeated-dose protocols should account for accumulation only where tissue half-life is genuinely long; for most peptides with short plasma half-life and rapid degradation, accumulation is not a practical concern.

For dose ranges in published research, see the dosing reference page. For reconstitution guidance, see the reconstitution reference page.