Selank is a lab made chain of seven amino acids, the small building blocks that proteins are made of. Short chains like this are called peptides. The first four of them are tuftsin, a fragment found in antibodies, the proteins the immune system uses, and three more amino acids were added at the tail so that the body's enzymes take longer to break the chain apart. Russia registered it with its Ministry of Health in 2009, and it is sold there as drops for the nose, for anxiety. It has not been approved anywhere else.
What it is supposed to do
Nobody has established what it does. The most quoted idea is that it slows the destruction of enkephalins, the body's own opioid like signals, and in a test tube it halved the activity of the enzyme that breaks them down. That was measured at a concentration of 20 micromolar in the fluid around the cells, which is not a dose anybody can put in a syringe, and turning one figure into the other needs a number for how widely the substance spreads through the body that has never been published for this peptide. The other place researchers have looked is GABA, the body's signal for damping brain activity down, which is what the sedatives used as the comparison drug in all three human trials work through. Of the three attempts there, one read which genes were switched on in the frontal cortex of rats, one used human tumour cells in a dish and found no detectable effect on the genes at all, and the only one that looked at the GABA docking points directly also used cells in a dish.
What people take it for
It is taken for anxiety. That is what Russia registered it for, and the human studies were run in patients with generalized anxiety, with neurasthenia, an older word for persistent exhaustion, and with phobias and anxiety disorders alongside physical symptoms that had no physical cause found. Online it is usually sold as one half of a pair with another peptide called Semax, and people run the two together, which is an arrangement of the market rather than anything a study has tested.
The dose question
What circulates
900 mcg a day from the drops, 1,350 quoted by vendors
What was studied
No trial has ever reported a dose
Three Russian trials, 192 patients, no dose in any of them
There is nothing to compare against. None of the three trials reports a dose or a treatment length, so both circulating numbers came from somewhere other than a study: 900 mcg per day is a derivation from assuming 20 drops to a millilitre of the Russian nasal drops, and the 1,350 mcg per day that vendors attribute to the 2008 trial is absent from every primary source.
Reported because it is what people use. Nothing here recommends any amount.
How long it lasts
No half life has been published in a person. The only figure of that kind anywhere in the record is on the Russian label, which describes the substance clearing the blood within about five minutes.
Route studied
Up the nose, as drops. Every documented human use is by that route.
Route used
Injected. The injectable solution that is actually sold has never been compared with the nose drops in a clinical study.
How to check you have the right molecule
This entry publishes no molecular weight to hold a lab report against, so the check is the order of the seven building blocks. Selank reads Thr-Lys-Pro-Arg-Pro-Gly-Pro. Semax, the compound it is sold beside, reads Met-Glu-His-Phe-Pro-Gly-Pro, and the two share only the last three, so a certificate that prints a sequence tells you at once which of the pair is in the bottle. The second check costs nothing and catches a different kind of fake. Search the United States government trials registry at ClinicalTrials.gov for Selank, by intervention, by term and by exact quoted term, and you get no Selank trials at all. Every record on that registry carries an identifier beginning with the letters NCT, so any NCT number you are shown for a Selank trial is fabricated, and you can check that yourself in about ten seconds.
The costly mistake is the Semax pairing, because it is not a stack anybody has studied. Search for both names and you get 11 articles, and in none of them did researchers give both peptides to the same subjects. The one study that contains both names does the opposite of what a stack implies: Panikratova 2020 scanned 52 healthy people in three separate arms, one given Semax, one given Selank and one given nothing. The two are chemically related, sharing the last three of their seven building blocks, and that shared tail is a plausible route to a shared mechanism, which is a reason two compounds that act alike may not add up to more when taken together rather than an argument for combining them. Nobody has checked.
What is known about harm
The Russian instructions say the drug is not to be used in pregnancy or while breastfeeding and is not indicated under the age of 18, with no effectiveness or safety data in any of those groups. The 2014 trial in 60 patients reported minor impairments of thinking alongside a strong effect on anxiety. Past that, the honest answer is that nobody has looked. There is no safety data and no blood level data for the injected route in any species, and the published record stops at two weeks, which is where the Russian treatment course ends.
Everything on this page is a summary. The citations, the studies and the reasoning live in the full entry.