PT-141 (Bremelanotide) half-life & pharmacokinetics

Reported half-life

Approximately 2.7 hours plasma half-life after subcutaneous administration. Functional sexual-arousal effects emerge within 45-60 minutes of administration and persist for approximately 4-6 hours. Vyleesi is licensed as an on-demand (as-needed) treatment rather than daily chronic administration, reflecting the acute rather than sustained mechanism of central MC4R activation.

The half-life and pharmacokinetic profile of PT-141 (Bremelanotide) 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 (Vyleesi licensed route — pre-filled autoinjector pen)
• Intranasal (earlier clinical development route; discontinued for Vyleesi)

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 melanocortin-receptor agonist (non-selective across MC receptors but optimised for MC4R central sexual-function activation); FDA-licensed medicinal product for HSDD in premenopausal women.

Mechanism context

Half-life interpretation depends on the underlying mechanism. PT-141 (Bremelanotide) acts as follows:

PT-141 (bremelanotide) is a cyclic heptapeptide (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH) developed by Palatin Technologies through systematic medicinal chemistry optimisation of Melanotan II, which was itself a stabilised cyclic analogue of α-MSH. The molecular design goal was to preserve the central-nervous-system sexual-function effects of Melanotan II while reducing the pigmentation activity through modified MC1R engagement. The result is a compound with retained agonism at MC3R, MC4R, and MC5R with reduced but still-present MC1R activity — a relative receptor-selectivity shift toward the central sexual-function receptors.

See the full PT-141 (Bremelanotide) 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.