Selank

1. 01Elsewhere

   Absorbed through the lining of the nose

   In Russia, Selank is dropped into the nose. The label says it passes through the nasal lining into the blood within about half a minute and that some of it reaches the brain.

   For experts

   The Russian label reports absolute bioavailability of 92.8% after intranasal administration, detection in plasma at 30 seconds, rapid distribution to tissues and penetration into brain tissue. These figures come from the manufacturer's registered label; the underlying study was not located, and no independent human pharmacokinetic paper was found. Researchers chose the intranasal route in rat studies because it is considered efficient for delivering peptides to the central nervous system.[src][src]

2. 02Bloodstream

   Broken down within minutes

   Peptides like this are chopped up quickly by enzymes in the body. The label says Selank fades from the blood within a few minutes and none is found in urine. The extra three amino acids were added to make it last longer than its parent, tuftsin.

   For experts

   The Pro-Gly-Pro extension was designed to improve metabolic stability and give a longer duration of action than tuftsin. The Russian label states that plasma concentration declines progressively over about 5 to 5.5 minutes and that neither unchanged drug nor metabolites are found in 24-hour urine, attributed to rapid degradation by tissue peptidases. This is a label statement, not a formally reported half-life. The fragment Gly-Pro has been reported to reproduce some Selank effects on gene expression in mouse spleen, so fragments may contribute to activity (animal data).[src][src][src]

3. 03Brain

   May nudge the brain's main calming signal (lab and animal data)

   The brain uses a chemical called GABA to calm nerve cells. In lab tests on rat brain tissue, Selank made GABA stick better to its target. In rats it also changed activity of many genes linked to GABA. This has not been shown to happen in people, and one cell test found no direct effect.

   For experts

   In radioligand binding on rat brain plasma membranes, Selank acted as a positive allosteric modulator of [3H]GABA binding, with a combined effect with some benzodiazepines that was not simply additive, and it could block the modulatory activity of diazepam and olanzapine in that assay (Vyunova et al., 2018). Intranasal Selank in male Wistar rats changed expression of 29 of 77 analysed neurotransmission genes in frontal cortex at 1 h and 17 at 3 h (45 and 22 when Selank and GABA results are pooled), and changes at 1 h correlated positively with those after GABA itself (Volkova et al., 2016). In human IMR-32 neuroblastoma cells Selank alone did not change GABAergic gene mRNA levels but altered the effect of GABA and olanzapine on them (2017). All of this is animal or in vitro; direct GABA-A receptor modulation in humans has not been demonstrated.[src][src][src]

4. 04Bloodstream

   May slow the breakdown of the body's own painkilling peptides

   The body makes small molecules called enkephalins that help handle stress and pain, and enzymes break them down. In blood samples in the lab, Selank slowed those enzymes. People with generalized anxiety disorder (constant, hard-to-control worry) had enkephalins that were cleared faster than normal.

   For experts

   In blood plasma in vitro, Selank inhibited enkephalin hydrolysis in a concentration-dependent way (IC50 15 microM) and was more potent than bacitracin and puromycin; patients with generalized anxiety disorder, but not panic disorder or agoraphobia, had a shortened enkephalin half-life and reduced total enkephalinase activity in blood (Zozulya et al., 2001). In the 62-patient GAD/neurasthenia study, leu-enkephalin half-life was reduced at baseline, correlated with anxiety, asthenia and autonomic symptoms, and rose during Selank treatment, mostly in patients with GAD (Zozulia et al., 2008). This is an association in small studies; a causal route to the clinical effect is not proven.[src][src]

5. 05Brain

   Changes in a brain growth factor in rats

   BDNF is a protein that helps brain cells grow and connect. In rats given alcohol for many months, Selank prevented a rise in BDNF in two brain areas and protected memory. This is animal-only work.

   For experts

   In outbred rats drinking 10% ethanol for 30 weeks, intraperitoneal Selank for 7 days prevented ethanol-induced memory and attention disturbances in the object recognition test and prevented the ethanol-induced increase of BDNF content in hippocampus and frontal cortex measured ex vivo (Kolik et al., 2019). Effects on BDNF have not been shown in humans.[src]

6. 06Immune system

   Shifts immune signals in animals and blood samples

   Selank comes from an immune-system fragment, and it seems to touch the immune system too. In mice it changed the activity of dozens of inflammation-related genes. In blood from people with anxiety it shifted some immune messengers. What this means for health is unknown.

   For experts

   In mouse spleen after a single intraperitoneal injection, Selank changed expression of 34 of 84 inflammation-related genes, with Bcl6 altered by Selank and its fragments (Kolomin et al., 2011). In human blood, 14 days of Selank in patients with GAD and neurasthenia was associated with shifts in the Th1/Th2 cytokine balance, and in vitro Selank suppressed IL-6 gene expression in blood cells from patients with depression but not from healthy controls, while the same abstract reports a rise in IL-6 concentration in patients' blood-cell cultures with Selank (Uchakina et al., 2008). These are small studies with no clinical immune endpoints.[src][src]

7. 07Brain

   What small human studies report on anxiety

   In one small Russian study, people with anxiety improved about as much on anxiety tests with Selank as with an older anti-anxiety medicine (medazepam). Other small studies compared it with, or added it to, phenazepam. These were small studies without the strong design of large modern trials, so the results are early.

   For experts

   In 62 patients with GAD and neurasthenia, Selank (n=30) and medazepam (n=32) had similar anxiolytic effects on Hamilton, Zung and CGI scales, and Selank additionally showed antiasthenic and psychostimulant effects (Zozulia et al., 2008). In 60 patients with phobic-anxiety and somatoform disorders, a comparison with phenazepam reported pronounced anxiolytic and mild nootropic effects of Selank, with the anxiolytic effect lasting a week after the last administration; the abstract gives no comparative figures (Medvedev et al., 2014). In 70 patients (40 on Selank plus phenazepam, 30 on phenazepam alone), the combination gave an earlier effect on HDRS and fewer phenazepam side effects than phenazepam alone (Medvedev et al., 2015). Blinding and placebo control are not described in the abstracts, and no replication outside Russia was found. In rats, Selank plus diazepam gave the largest reduction in anxiety under chronic mild stress (Kasian et al., 2017; animal only).[src][src][src][src]

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