Selank

Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its first four residues are tuftsin, an endogenous immunomodulatory tetrapeptide released from the Fc fragment of immunoglobulin G. The added Pro-Gly-Pro tail is not decorative: it protects the molecule from rapid enzymatic cleavage and extends its duration of action long enough to be useful. Selank was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences with the Zakusov Institute of Pharmacology, and it is registered in Russia as an anxiolytic nasal solution.

The primary appeal of Selank is that it produces anxiolysis without the trade-offs of benzodiazepines. In a 2008 trial in patients with generalized anxiety disorder and neurasthenia, Selank produced anxiolytic and antiasthenic effects comparable to medazepam, but without sedation, cognitive slowing, muscle relaxation, or a withdrawal syndrome on discontinuation. That profile, calm without dulling, is why it is classified as an anxiolytic nootropic rather than a sedative.

Mechanistically Selank works on several fronts rather than binding one receptor hard. It inhibits enkephalin-degrading enzymes in plasma, raising levels of endogenous enkephalins (Bull Exp Biol Med 2001), which is one proposed route to its anxiolytic effect. It alters expression of genes involved in GABAergic neurotransmission, including GABA-A receptor subunits, in both human cell lines and rat brain (Front Pharmacol 2016). Intranasal administration upregulates BDNF expression in the rat hippocampus (Dokl Biol Sci 2008), and it shifts serotonin turnover in the brain in a way that differs from plain tuftsin.

Route matters more with Selank than with most research peptides. The registered Russian product is a 0.15% nasal solution (1.5 mg/mL), and intranasal delivery is the route nearly all the human data uses. Glyproline-containing peptides given intranasally reach brain tissue quickly, which is why the standard clinical schedule is a few drops per nostril two or three times a day rather than a single injection. Subcutaneous administration is used in animal and self-directed research, but it is not the route the clinical dosing was established on.

Practical handling: Selank is supplied lyophilized, usually in 5 mg or 10 mg vials. A 5 mg vial with 2 mL of diluent gives 2.5 mg/mL, so a 500 mcg dose is 0.2 mL, which is 20 units on a U-100 insulin syringe. For nasal use, many researchers reconstitute to a known mg/mL and dispense with a metered spray (a typical nasal pump delivers 0.05 to 0.1 mL per actuation), then calculate mcg per spray from the concentration. Bacteriostatic water is standard for injection, but its 0.9% benzyl alcohol can irritate nasal mucosa, so sterile saline is often preferred for nasal preparations at the cost of a much shorter usable window. Selank is not FDA-approved and is sold in the United States for research purposes only.