Reference

Last reviewed: 28 Apr 2026
Sources cited: 9
Residues: 7

Primary structure7 residues · 751.9 Da

01ThrThreonine

02LysLysine

03ProProline

04ArgArginine

05ProProline

06GlyGlycine

07ProProline

Nonpolar Polar Acidic Basic Aromatic Gly/Pro

Selank

Last verified: 2026-04-23

At a glance


Also known as	TKPRPGP (sequence), tuftsin-derived anxiolytic
Class	Synthetic heptapeptide, tuftsin analogue, anxiolytic / nootropic
Typical route	Intranasal only (drops or spray)
Plasma half-life	~25 minutes (standard Selank); 2.5–4 hours (N-Acetyl Selank Amidate)
Duration of effect	BDNF upregulation persists 48–72 hours; dendritic changes 5–7 days; cytokine effects 7–14 days post-cessation
Molecular weight	751.9 Da
Sequence	Thr-Lys-Pro-Arg-Pro-Gly-Pro (7 amino acids) — derived from the natural immune peptide tuftsin

What it is

Selank is Semax’s sibling compound — developed at the same Russian Institute of Molecular Genetics, also a synthetic heptapeptide, also registered as a medicine in Russia, also usually dosed intranasally. But they do different things.

Where Semax is stimulating and focus-oriented, Selank is calming and anxiolytic. It was originally derived from tuftsin, a naturally occurring immunoregulatory peptide, and then modified for stability. It’s approved in Russia for generalised anxiety disorder and neurasthenia (a diagnostic category still used in Russian psychiatry, roughly corresponding to chronic fatigue with anxiety and cognitive complaints).

The clinical comparison that matters: Russian trials have shown Selank produces anxiolytic effects comparable to benzodiazepines — without sedation, without cognitive impairment, without dependence, and without withdrawal. If true and replicable outside Russia, that would be a significant pharmacological find. That “if” is doing a lot of work — see the evidence section.

Mechanism

Selank’s effects are unusually well-characterised for a biohacker-space peptide, largely because of the Russian research effort.

GABA-A modulation. Selank binds to GABA-A receptors and allosterically modulates their activity — conceptually similar to how benzodiazepines work, but without producing sedation or dependence. A transcriptomic study showed Selank altered expression of 45 of 84 GABA-neurotransmission genes in the rat frontal cortex within an hour of administration.1
BDNF upregulation. Like Semax, Selank rapidly elevates BDNF in the hippocampus. The anxiolytic and neurotrophic mechanisms reinforce each other.2
Enkephalinase inhibition. Selank inhibits breakdown of endogenous enkephalins, contributing to mood and stress-response effects.
Serotonergic modulation. Documented changes to serotonin metabolism, though less central than the GABA and BDNF effects.
Immune modulation. As a tuftsin derivative, Selank has documented effects on cytokine profiles — notably shifting Th1/Th2 balance and modulating interleukin expression. This is both interesting (possible immune benefit in chronic low-grade inflammation) and worth flagging (unpredictable effects in dysregulated immune systems).3

The active PGP metabolite (same as Semax) contributes to the extended duration of effect. Both peptides metabolise to Pro-Gly-Pro, which is pharmacologically active in its own right.

Routes of administration

Like its sibling Semax, Selank is effectively intranasal-only in practice. The same pharmacological logic applies: short plasma half-life, nose-to-brain delivery is the whole point.

Intranasal (drops or spray)


Bioavailability to CNS	60–70% via direct olfactory pathway transport
Onset	15–30 minutes subjective anxiolytic effect
Duration	4–6 hours of acute anxiolytic effect per dose; BDNF and cytokine effects persist 48+ hours
Typical dose (this route)	100–500 mcg per administration, 1–3× daily (or PRN)
Equipment	0.15% solution, calibrated nasal spray or dropper bottle
When this route makes sense	Every use-case. The only route with meaningful evidence and community validation.

The intended route. Same nose-to-brain mechanism as Semax — the peptide reaches CNS directly via olfactory and trigeminal nerves, bypassing the plasma clearance problem. Many users dose as needed (PRN) for acute anxiety, which works well with this route’s relatively fast onset.

Subcutaneous / intramuscular injection


Bioavailability to CNS	Low — must cross blood-brain barrier from plasma, and clearance is rapid
Onset	Not well characterised for anxiolytic indication
Typical dose (this route)	Not recommended for typical use-cases
When this route makes sense	A small number of Russian clinical protocols have used injection for specific indications (immune modulation in chronic infection patients, for example). For anxiolytic use, injection offers no clear advantage and loses the direct CNS targeting.

Some of the Russian immunomodulatory research used injection routes because the target was peripheral immune cells, not CNS. For the anxiolytic/nootropic use that drives biohacker interest, injection is off-pattern.

Oral / sublingual


Bioavailability	Negligible. Rapid GI degradation.
Typical dose (this route)	Not recommended
When this route makes sense	Never, practically.

As with Semax, oral Selank has no meaningful bioavailability. The peptide is broken down in the gut. Any reported sublingual effect is likely partial nasal absorption via the nasopharynx.

N-Acetyl Selank Amidate (NASP) — same routes

The acetylated variant extends plasma half-life from ~25 min to 2.5–4 hours but uses the same intranasal route. It does not unlock a useful oral route. It is dosed less frequently (1–2× daily vs 2–3×) but is otherwise administered identically.

Cross-route comparison

Intranasal, or not at all. Selank’s pharmacology doesn’t offer a reasonable alternative route for the anxiolytic/nootropic use-case that drives 95% of community interest. If intranasal dosing is contraindicated (severe septal issues, preservative reactivity), consider alternative anxiolytic approaches rather than attempting an off-pattern route.

PRN vs scheduled use is the more important route-adjacent decision. Some users take Selank only when acute stress or anxiety emerges; others run a scheduled 14-day course. Both patterns have Russian clinical precedent.

What the evidence says

Honest summary: genuine clinical data from Russia, almost no Western replication, the Nature-journal evidence base is thin.

Russian clinical trials:

62-patient GAD trial (2008) — randomised comparison of Selank against medazepam (a benzodiazepine). Both produced comparable anxiety reduction; Selank group did not show sedation, cognitive impairment, or dependence markers. This is the most-cited study for Selank.4
Neurasthenia protocols — multiple Russian studies in anxiety-asthenic presentations, reporting both anxiolytic and mild stimulating effects (the “psychostimulant” language in translated abstracts tends to mislead Western readers; the effect is much milder than pharmaceutical stimulants).
Immunomodulatory effects — Russian studies in patients with chronic infections and immune dysregulation, reporting cytokine profile normalisation.3
Registered indications in Russia: generalised anxiety disorder, neurasthenia.

Western evidence base:

Essentially none at the clinical level. No Western RCTs have replicated the GAD findings.
English-language mechanism papers exist (GABA, BDNF, gene expression studies in animal models) and are the main bridge between Russian clinical claims and Western neuroscience.
A 2020 functional connectivity study examined Selank and Semax effects on brain networks.5

Community evidence:

Selank is reported as a relatively gentle anxiolytic — users describe “taking the edge off” without feeling drugged. It’s genuinely popular among people who’ve tried benzodiazepines and disliked the sedation/dependence profile, and among people who use SSRIs and want acute PRN relief without layering more medication.
Non-response is real. A meaningful minority of users report little or no effect. This is consistent with Russian studies noting fast vs slow responders.

FDA position: In 2023 the FDA specifically flagged concerns about compounded Semax and Selank around limited human safety information, immunogenicity, aggregation, and peptide-related impurities.6 This is the formal basis for current US regulatory posture.

Typical use patterns

Observations, not recommendations.

Dose:

Standard: 200–400 mcg per dose, 2–3 times daily intranasally
Russian clinical (GAD): 250–300 mcg three times daily for 14 days
Acute anxiety PRN: 250–500 mcg, onset 15–30 minutes, useful window ~4–6 hours
Microdose: 100 mcg in the morning for general stress resilience without sedation

Timing:

Anytime — unlike Semax, Selank doesn’t disrupt sleep. Many users dose in the evening specifically for sleep onset.
Effects typically felt within 15–30 minutes
Used acutely for stress peaks (before meetings, social events, flights) — many users describe it as a “benzo substitute without the downsides”

Cycle:

Russian clinical protocols: 14-day courses
Community use: continuous daily dosing is common and reportedly well-tolerated — tolerance does not appear to develop quickly, if at all, unlike benzodiazepines
Long-term chronic dosing (>30 days) is not characterised in published literature outside Russian practice

Stacking:

Semax + Selank is the classic stack. Semax for focus in the morning, Selank for calm throughout the day. Often co-administered as a single morning dose for “engaged calm” — alert without being wired.
Sometimes stacked with adaptogens (Rhodiola, ashwagandha) for layered stress resilience
Some users replace or supplement L-theanine with Selank
N-Acetyl Selank Amidate (NASP) and N-Acetyl Semax Amidate (NASA) are the modified-variant versions sometimes used together — longer duration, less frequent dosing, similar subjective effects

For sensitive systems

Selank’s profile is more forgiving than Semax for sensitive populations — but it has its own considerations.

Start dose. 100 mcg once daily in the morning. Hold 3–5 days before increasing.

Ramp. If tolerated, increase to 200 mcg once daily, then to twice daily (morning + afternoon). Because Selank is calming rather than stimulating, the ramp issue is less about nervous system over-activation and more about subjective sensitivity (some sensitive users feel too calm, flat, or dissociated at higher doses).

Expected adjustment profile:

Mild headache (uncommon, route-related)
Nasal irritation, dryness, or mild burning — same as any intranasal peptide
Mild transient fatigue or “foggy calm” — less common than Semax’s over-stimulation, but worth naming. Some sensitive users feel drowsy or emotionally flat for the first few doses before settling.
Sinus irritation, occasional sore throat (post-nasal drip effect)

Why Selank may be genuinely useful for this audience:

GABA-A modulation without sedation or dependence is a pharmacologically interesting profile for people who can’t tolerate benzodiazepines (common in MCAS — many benzos contain excipients that trigger reactions) or want to avoid dependence on SSRIs
Immune-modulating effects via tuftsin derivation may complement rather than provoke sensitive immune systems — unlike BPC-157, which can trigger initial mast cell flares
Non-sedating anxiolysis is valuable for people managing anxiety on top of POTS, long COVID, or chronic fatigue, where benzodiazepine sedation is disabling

What’s not normal and warrants stopping: significant mood flattening, dissociation-like symptoms, paradoxical anxiety (rare but reported in benzo-sensitive individuals — the GABA-A mechanism is shared), or worsening of baseline symptoms.

What to have on hand:

Saline nasal rinse for the irritation
Your usual antihistamines if you’re reactive to preservatives in commercial sprays

Interactions worth considering in sensitive populations:

Benzodiazepines: shared GABA-A mechanism. Layering is not advisable without specific clinical guidance. Users attempting to taper off benzodiazepines sometimes use Selank as a bridging tool — this is unsupervised territory and outside what any published literature addresses.
SSRIs/SNRIs: no documented interaction. Many community users report Selank is a useful adjunct to SSRI therapy for acute anxiety episodes.
Alcohol: additive GABAergic effect theoretically. Not well studied.
LDN (Low Dose Naltrexone): common in MCAS/autoimmune populations. No documented interaction; Selank’s enkephalinase-inhibition mechanism has theoretical overlap with opioid-system modulation but no reported clinical issue.
Stimulant ADHD medication: stacks well in community reports — Selank takes the edge off stimulant-induced anxiety.

PMDD note: Selank may be particularly relevant here. PMDD has GABA-system involvement (luteal-phase GABA receptor sensitivity shifts), and Selank’s non-benzodiazepine GABA modulation is the kind of intervention that fits the pathophysiology. No specific research exists. This is mechanism-guided speculation worth tracking, not established use.

Reasonable expectations

Onset. Acute anxiolytic effect typically reported within 15–30 minutes, peaking at 1–2 hours, noticeable for 4–6 hours on a single dose. Effects of a consistent protocol (baseline anxiety reduction, better stress tolerance) accumulate over 1–2 weeks.

Response rate. Roughly 60–70% of users report clear subjective benefit in community surveys. Non-response is real — 25–30% describe feeling nothing. This is consistent with the “fast vs slow responders” language in Russian clinical literature.

What the literature actually supports.

Generalised anxiety disorder (Russian clinical trial data): reasonable evidence, not independently replicated Westward
GABA-A modulation (animal + cell-line mechanism): well-established
Non-sedating, non-dependence-forming anxiolytic profile: strongly supported by available data, but “available data” means one 62-patient trial, not the large-RCT evidence base you’d want
Immune modulation (Russian studies in chronic infection populations): interesting signal, unreplicated

What not to expect.

A benzodiazepine substitute for severe anxiety or panic disorder. Selank’s effect is gentler — more “calm floor” than “off-switch.”
Rapid onset for panic attacks. By the time it kicks in, an acute panic episode is typically past peak.
A stimulant. Despite some translated sources describing “psychostimulant effects,” this is a translation artefact; the effect is mild stress-resilience enhancement, not caffeine-like activation.
A mood antidepressant. Selank is anxiolytic; it does not reliably elevate depressed mood.
Freedom from concerns about GABA-system medications. Shared-mechanism interactions matter.

Cost

Approximate as of April 2026, research-chemical market, UK-focused. Vendor-neutral.


0.15% nasal drops / spray (3 mL bottle, ~4.5 mg total)	£30–55
N-Acetyl Selank Amidate (NASP) 0.15% spray	£40–65
Cost per month, community-standard (400 mcg × 2 daily)	~£20–35
Cost per month, sensitive-start (100 mcg/day)	~£8–15
Cost per Russian-protocol 14-day cycle (300 mcg × 3 daily)	~£20–30

Selank is typically slightly more expensive per mg than Semax in the UK research-chemical market. NASP (the acetylated variant) commands a premium for its longer duration.

Reconstitution

As with Semax, Selank is most often supplied pre-made as a 0.15% nasal solution. User-reconstitution from lyophilised powder is less common.

Standard preparation, 5 mg lyophilised Selank:

Dissolve in ~3.3 mL of saline or sterile water → 0.15% solution (1.5 mg/mL)
A 100 µL spray delivers ~150 mcg per actuation
For 300 mcg doses: 2 sprays (usually 1 per nostril)

Pump variability: same caveat as Semax. Measure your pump before trusting the dose. 50 µL / 100 µL / 140 µL pumps all exist. One drop from a standard pipette ≈ 50 µL.

Open the Vial Plan calculator

Areas of concern ⚠

Safety signals

Russian clinical use since 1994, approved for GAD and neurasthenia. More clinical history than most biohacker peptides.
Long-term safety (>30 days continuous use) outside Russian clinical practice is uncharacterised in peer-reviewed literature.
No documented dependence or withdrawal in human or animal studies. Genuinely reassuring given the GABAergic mechanism.
FDA (2023) explicitly flagged concerns for compounded Selank and Semax: limited human safety information, immunogenicity risk, aggregation, peptide-related impurities.6 This is the formal regulatory basis for the current US posture.

Shared-mechanism interaction risks

GABA-A modulation overlaps with benzodiazepines, z-drugs, barbiturates, and alcohol. Layering is theoretically risky even if Selank itself doesn’t cause sedation at its own doses.
Anyone tapering benzodiazepines or z-drugs should treat Selank as unverified territory, not a safe substitute

Paradoxical anxiety

Rare but documented in GABA-A modulators — some individuals experience increased anxiety rather than relief. If you’ve had paradoxical reactions to benzodiazepines, Selank may produce the same. Stop and reassess.

Immune modulation is a double-edged effect

In chronic low-grade inflammation, Selank’s cytokine-normalising effect may be beneficial.
In active autoimmune flare, in untreated immune deficiency, or in immunocompromise, the same mechanism is harder to predict.
Not a contraindication, but a reason for clinical-grade caution if you’re on immunosuppressants or biologics.

Route-specific issues

Nasal irritation, dryness, post-nasal drip, occasional sore throat are the most common community-reported issues
Preservative reactions (benzalkonium chloride, phenoxyethanol in commercial sprays) — relevant for reactive individuals

Quality and sourcing

Russian-origin commercial Selank (often sold as “Selank-Peptide” by Innovative Pharmaceutical Research, the Russian manufacturer) is generally considered higher quality than research-chemical reconstitutions
Research-chemical Selank varies widely in potency and purity; independent testing is rare
Storage: lyophilised Selank is stable at room temperature; reconstituted 0.15% solution should be refrigerated, used within 30–45 days

Populations where caution is warranted

Pregnancy and breastfeeding — no human data, default contraindication
Active autoimmune flare — immune-modulation uncertainty
Concurrent benzodiazepine use — shared mechanism, not a safe stack
History of paradoxical benzodiazepine reaction — may extend to Selank
Under 18 — studied paediatrically in Russia for anxiety, but not a compound with a clear evidence base for unsupervised use in this age group

FDA / regulatory status

Jurisdiction	Status	Last verified
US (FDA)	Not approved. FDA (2023) explicitly flagged compounded Selank for safety concerns. Not on 503A Category 1 list.	2026-04-23
UK (MHRA)	Not licensed. Not a controlled substance. Sold as research chemical with “not for human consumption” labelling.	2026-04-23
EU (EMA)	Not approved. Similar posture to UK.	2026-04-23
Russia	Approved medicine. Registered for generalised anxiety disorder and neurasthenia. Prescription drug.	2026-04-23
WADA (sport)	Not explicitly listed; treat as prohibited for tested athletes under general peptide/hormone category.	2026-04-23

Narrative. Same regulatory asymmetry as Semax: Russian-approved medicine, Western research chemical. The FDA’s 2023 flagging is more pointed for Selank than for some other peptides — specifically citing immunogenicity and aggregation concerns. This is not inconsistent with the GABA-A-modulating mechanism being real; it’s a comment on compounded product quality.

For UK readers: Selank is legally available as a research chemical from UK-based suppliers. Not a controlled substance. Possession for personal research use is not an offence. Sale for human consumption is not permitted.

What to track in Peptrax

Selank is taken for anxiety-adjacent calm without sedation, and the question worth answering is whether daily anxiety load actually drops over a 2–4 week cycle. The most useful daily log is a brief anxiety rating (morning and evening), a sleep quality note, and a one-line note on the day’s stress context — work pressure, conflict, social load. Without the context line, ratings drift around with what the day was rather than with what Selank is doing.

The on/off contrast is critical. Most users cycle Selank because tolerance develops, and the genuine signal lives in how a clean week compares to a Selank week. If a 2-week cycle ends and the next week feels indistinguishable, that is the honest read. Cycle dates, route (intranasal is dominant), and dose make the comparison possible.

For users with diagnosed anxiety disorders, the relevant log is symptom-specific: panic frequency, intrusive thoughts, social-situation tolerance — whatever your baseline pattern is. A generic “felt calmer” rating misses what actually changed. Logging whether Selank substituted for, complemented, or did nothing alongside existing treatment (SSRI, therapy, benzo PRN) is the question that matters for a real conversation with a clinician.

For personal tracking and informational purposes only — not medical advice.