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Semax

Evidence grade: Early human data

A Russian-developed ACTH fragment studied for attention, stroke recovery and BDNF expression, without the hormonal activity of ACTH itself.

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Selank

Evidence grade: Early human data

A tuftsin-derived anxiolytic peptide studied for generalised anxiety, with benzodiazepine-like calming reported without sedation or dependence.

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2 cited sources1 human studyReviewed 1 Jun 2026
2 cited sourcesNo human data on fileReviewed 1 Jun 2026

At a glance

At a glance compared across Semax, Selank
AttributeSemaxSelank
Primary useCognition & moodCognition & mood
Evidence gradeEarly human dataEarly human data
Human datadiffersYes — see citationsNo human citations on file
Cited sourcesdiffers2 sources · 1 human2 sources · 0 human
In one sentenceA Russian-developed ACTH fragment studied for attention, stroke recovery and BDNF expression, without the hormonal activity of ACTH itself.A tuftsin-derived anxiolytic peptide studied for generalised anxiety, with benzodiazepine-like calming reported without sedation or dependence.

Mechanism

Mechanism compared across Semax, Selank
AttributeSemaxSelank
How it is thought to workSemax is a synthetic fragment of adrenocorticotropic hormone with the hormonal portion removed. Within an hour of intranasal dosing, rodent studies show sharp increases in BDNF and its receptor TrkB in the hippocampus. It also appears to slow the breakdown of enkephalins and to modulate dopaminergic and serotonergic tone. In Russia it holds regulatory approval for stroke and cognitive indications; elsewhere it is unapproved.Selank is a synthetic analogue of the immune peptide tuftsin. It modulates GABA-A expression and appears to stabilise enkephalin levels by inhibiting their enzymatic breakdown. Russian trials also report shifts in serotonin turnover and in interleukin-6 expression, which is why it sits at the crossroads of the anxiety and inflammation literature.
What the research reports
  • Increased BDNF and TrkB expression in hippocampus (rodent, within 1h)
  • Improved attention and working memory in small human studies
  • Neuroprotection and functional recovery in ischaemic stroke trials conducted in Russia
  • Reduced anxiety-like behaviour without sedation in animal models
  • Anxiolytic effect comparable to medazepam in Russian comparative trials
  • No reported sedation, tolerance or withdrawal in those trials
  • Changes in IL-6 and other inflammatory markers
  • Improved attention alongside reduced anxiety, rather than at its expense
What it is NOT shown to do
  • No large multi-centre trial outside Russia has replicated the stroke results
  • Not demonstrated as a treatment for major depressive disorder
  • Long-term safety beyond a few months is uncharacterised
  • No Western regulatory trial has been conducted
  • Not established as a replacement for anxiety medication
  • Effects beyond short study windows are unknown

Dosing & pharmacology

Dosing & pharmacology compared across Semax, Selank
AttributeSemaxSelank
Routes studiedIntranasal, SubcutaneousIntranasal, Subcutaneous
Half-lifediffersVery short in plasma (minutes); central effects reported to outlast it considerablyShort in plasma; behavioural effects reported for several hours
Dose referenceResearch literature commonly reports 200–600 mcg/day intranasally, split across doses. Clinical stroke protocols used substantially higher amounts under supervision.Research literature commonly reports 250–900 mcg/day intranasally, usually split.
Typical study cyclediffersStudies typically run 10–14 days, then a breakStudies typically run 10–14 days

Chemistry & handling

Chemistry & handling compared across Semax, Selank
AttributeSemaxSelank
SequenceMet-Glu-His-Phe-Pro-Gly-Pro (MEHFPGP)Thr-Lys-Pro-Arg-Pro-Gly-Pro (TKPRPGP)
Molecular formuladiffersC37H51N9O10SC33H57N11O9
Molecular weightdiffers813.9 g/mol751.9 g/mol
CAS numberdiffers80714-61-0129954-34-3
Storage (reconstituted)2–8 °C, typically used within 2–4 weeks2–8 °C, typically used within 2–4 weeks

Risk

Risk compared across Semax, Selank
AttributeSemaxSelank
Reported side effects
  • Nasal irritation with intranasal use
  • Headache
  • Overstimulation or irritability at higher amounts
  • Sleep disruption if dosed late in the day
  • Nasal irritation
  • Mild fatigue or flatness in some users
  • Headache
Contraindications
  • Pregnancy and breastfeeding
  • Uncontrolled anxiety or bipolar disorder — stimulating effects can destabilise
  • Concurrent MAOIs or stimulants without clinical oversight
  • Pregnancy and breastfeeding
  • Do not use to self-taper off prescribed benzodiazepines without clinical supervision

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