Selank half-life & pharmacokinetics

Reported half-life

Very short plasma half-life (~minutes) due to rapid peptidase degradation; functional pharmacology dominated by intranasal delivery achieving direct CNS access. Functional anxiolytic and modest cognitive effects from a single intranasal dose persist for 4-12 hours, longer than Semax effects despite similar plasma half-life — attributed to downstream effects on enkephalin and monoamine system tone that persist beyond peptide presence.

The half-life and pharmacokinetic profile of Selank 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

• Intranasal (standard research and clinical route)
• Subcutaneous injection (pre-clinical research)

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

Synthetic heptapeptide tuftsin analogue; anxiolytic and modest nootropic compound with GABAergic, serotonergic, and enkephalinase-inhibitory mechanisms.

Mechanism context

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

Selank is a 7-amino-acid synthetic heptapeptide (Thr-Lys-Pro-Arg-Pro-Gly-Pro, TKPRPGP) derived from tuftsin — an endogenous immunomodulatory tetrapeptide (Thr-Lys-Pro-Arg) generated by enzymatic cleavage of the Fc fragment of IgG by the spleen-derived enzyme leukokininase. The native tuftsin sequence is rapidly degraded by serum peptidases (half-life of minutes); Selank's C-terminal Pro-Gly-Pro tripeptide extension confers proteolytic stability through the same molecular strategy used for Semax, retaining the bioactive tuftsin pharmacophore while extending duration of action.

See the full Selank 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.