In-depth comparison
Selank vs Semax: the long answer
Selank is an anxiolytic + immunomodulator peptide: calms anxiety, supports mood, no sedation. Semax is a cognitive enhancer: focus, memory, BDNF + dopamine modulation. Both are Russian-developed heptapeptides, intranasally bioavailable, with 25+ years of clinical use in Russia (semax is on their Vital Drug List). Different jobs. Pick by goal, or use both on rotation.
Last reviewed: May 17, 2026
Mechanism: different targets, same form factor
Both are derived from the ACTH(4-10) fragment but optimized for different effects. Selank modulates GABA system + enkephalin levels: calming without sedation, anxiolytic without benzodiazepine-class side effects. Semax acts on BDNF expression (rapid + sustained upregulation), dopamine D2/D4 receptors, and acetylcholine pathways: focus, working memory, and neuroprotection. Both are heptapeptides, both work intranasally (peptide that crosses the nasal-CSF axis), both have 15-30 minute onset.
- Selank: Heptapeptide. GABA + enkephalin modulation. Anxiolytic without sedation.
- Semax: Heptapeptide. BDNF + dopamine + acetylcholine. Cognitive enhancement.
- Shared properties: Both intranasal, 15-30 min onset, 2-6 hour duration, Russian clinical heritage
What each is best for
Selank dominates for: generalized anxiety, social anxiety, sleep onset (without next-day grogginess), immune modulation during high-stress periods, alcohol/benzo tapering support (animal data). Semax dominates for: focus work sessions, post-stroke rehabilitation (Russian clinical indication), ADHD-adjacent focus issues, exam-prep cognitive endurance, and BDNF-related neuroplasticity goals. Many users run both: semax in the morning for focus, selank in the evening for wind-down.
- Selank wins on: Anxiety, social discomfort, sleep onset, stress-period immune support
- Semax wins on: Focus, working memory, post-stroke recovery, BDNF/neuroplasticity goals
- Common dual-use pattern: Semax morning (focus), selank evening (wind-down). Different times, no interaction concerns
Dosing: intranasal sprays, dose per nostril
Selank standard protocol: 250-500 mcg per nostril, 1-2x/day (morning and/or before stressful event). Semax: 100-300 mcg per nostril, 1-2x/day. Both work as 1% (semax) or 0.15-0.3% (selank) intranasal solutions. Calculate per-spray volume to hit target dose. N-acetyl variants (N-acetyl semax, N-acetyl selank) have extended half-life (3-4x longer) and slightly higher cost; the dose math is the same, but 1x/day works for most users.
- Selank dose: 250-500 mcg per nostril, 1-2x/day. N-acetyl variant: 250-500 mcg 1x/day
- Semax dose: 100-300 mcg per nostril, 1-2x/day. N-acetyl variant: 100-300 mcg 1x/day
- Onset: Both: 15-30 min to peak effect, 2-6 hour duration. N-acetyl: 4-8 hour duration.
Safety: exceptionally clean profile
Both have 25+ years of Russian clinical use (selank since 1990s, semax on Russia's Vital Drug List). Reported side effects in Russian clinical literature: mild fatigue (selank, rare), brief headache or sinus irritation from the spray (both, common in week 1, resolves). No published evidence of dependence, tolerance, or withdrawal, which matters given how cleanly selank competes with benzodiazepines for the anxiolytic use case. Neither is FDA-approved in the US.
- Selank side effects: Mild fatigue (uncommon), sinus irritation week 1 (common, resolves). No dependence/tolerance reported.
- Semax side effects: Brief headache or hyper-focus jitter, sinus irritation. Rare paradoxical fatigue if dosed too late.
- Tolerance / dependence: Neither has documented tolerance, dependence, or withdrawal in 25+ years of Russian clinical use
Cost: both inexpensive vs comparable alternatives
Research-use selank runs $40-80 for a 10mg vial; at 500 mcg/day that's ~30-50 days of supply = $1-3/day. Research-use semax similar: $40-90/10mg vial, similar daily cost. N-acetyl variants run 30-50% premium for the extended half-life. Compared to off-label modafinil or prescription anxiolytics, both are an order of magnitude cheaper.
- Selank cost: $40-80/10mg vial → ~$1-3/day at 500 mcg dose
- Semax cost: $40-90/10mg vial → ~$1-3/day at 300 mcg dose
- N-acetyl premium: 30-50% more per vial but ~2x duration → similar effective daily cost
Who chooses which
Pick selank if your primary issue is anxiety, racing thoughts, or stress reactivity. Pick semax if your primary issue is focus, mental endurance, or post-injury/stroke cognitive recovery. Pick both if you have anxiety AND focus issues (very common combo): semax morning for execution, selank evening for wind-down. N-acetyl variants are worth the premium if you don't want 2x daily dosing.
- Choose selank if: Primary issue is anxiety, social discomfort, or stress reactivity
- Choose semax if: Primary issue is focus, mental endurance, or BDNF/neuroplasticity goals
- Choose both if: Anxiety + focus issues (semax morning, selank evening, no interaction)