N-Acetyl Semax Amidate vs Selank
Doubly modified ACTH(4-7) analogue heptapeptide with potent nootropic, neuroprotective, and neurotrophic properties acting through BDNF/NGF upregulation and transcriptome-level modulation of inflammatory and neurotransmitter gene networks
A clever brain-boosting peptide derived from your immune system's natural tuftsin molecule—it calms anxiety and sharpens your mind without the drowsiness or addiction risks of traditional anti-anxiety medications [1][4].
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team · Editorial standards
Quick comparison
Dose range
N-Acetyl Semax Amidate
300–600 mcg/day
Selank
900–2700 mcg/day
Frequency
N-Acetyl Semax Amidate
Once daily
Selank
3 times daily
Administration
N-Acetyl Semax Amidate
Intranasal spray
Selank
Intranasal
Cycle length
N-Acetyl Semax Amidate
8-12 weeks
Selank
14 days, repeatable after 1-3 weeks
Onset speed
N-Acetyl Semax Amidate
Rapid (hours to days)
Selank
Rapid (hours to days)
Evidence level
N-Acetyl Semax Amidate
Moderate human trials (Phase 1-2)
Selank
Limited human trials
Benefit ratings
Brain Protection
Memory & Learning
Focus & Attention
Anxiety Relief
Cognitive Enhancement
Immune Support
Compound specifications
N-Acetyl Semax Amidate
Molecular formula
C39H54N10O10S
Molecular weight
855.0 g/mol
Half-life
Extended compared to native Semax; parent Semax has a plasma half-life of minutes, but pharmacological effects persist for hours due to intracellular signaling cascade initiation. N-Acetyl Semax Amidate achieves significantly longer effective duration
Bioavailability
Enhanced intranasal and subcutaneous bioavailability compared to native Semax; dual terminal modifications prevent enzymatic degradation from both ends
CAS number
Not assigned (N-Acetyl Semax Amidate); 80714-61-0 (parent Semax)
Selank
Molecular formula
C33H57N11O9
Molecular weight
751.9 g/mol
Half-life
2-3 minutes (plasma); effects last hours due to downstream signaling
Bioavailability
High intranasal absorption; near 100% subcutaneous
CAS number
129954-34-3
Dosing compared
N-Acetyl Semax Amidate
Intranasal
200-300 mcg/day
Divided 2-3 times daily · 2-4 weeks
Lower cognitive-use range with the 0.1% intranasal solution; Russian clinical protocols [6].
300-600 mcg/day
Divided 2-3 times daily · 2-4 weeks per course
Daily intranasal range used for cognitive enhancement with 0.1% Semax in Russian clinical practice; Semax upregulates BDNF/NGF [1][6].
Selank
Intranasal
Registered label dose
900 mcg/day total (3 doses of 300 mcg)
2 drops in each nostril, 3 times daily · Registered label dose
The approved dose on the Russian registration (ЛРС-003338/09): 2 drops in each nostril, three times a day. At 75 mcg per drop that is 300 mcg per administration and 900 mcg across the day, taken as a 14-day course that can be repeated after 1-3 weeks [7]. Human evidence, registered label.
Highest dose studied
2,700 mcg/day total (3 doses of 900 mcg)
900 mcg (12 drops) 3 times daily · Highest dose studied
The top of the range the developing institute describes as optimal — single doses of 300-900 mcg, 900-2,700 mcg a day split across three administrations — and the dose used in the multicentre generalised-anxiety and neurasthenia trial, where 2,700 mcg/day was compared against medazepam 30 mg/day for 14 days [9]. Because the label caps a single administration at 2-3 drops per nostril, a 900 mcg dose is given as 2-3 drops per nostril with the rest 15 minutes later [7]. Human evidence, trial protocol.
Subcutaneous injection
Community suggestion — not a studied protocol
300-500 mcg per injection
Once daily · Community suggestion — not a studied protocol
Community-reported, not peer-reviewed. No human study has tested subcutaneous selank and the registered product is nasal drops only [7], so this range comes from community and clinical-practice reports rather than a trial — there is no published safety or effectiveness data behind it. Two things worth knowing before choosing the route. The nasal spray is absorbed almost completely, with 92.8% of the dose reaching the bloodstream within 30 seconds [7], so injecting is not a way to get more of the peptide in. And in mice, the injected and intranasal routes did not act the same: injection shifted GABA-receptor binding while the nasal route shifted NMDA-receptor binding instead, which the authors put down to how each route is absorbed and broken down [13]. That is animal work, and no one has checked whether the same split happens in people.
Best suited for
N-Acetyl Semax Amidate
Cognitive enhancement through BDNF and NGF-mediated neuroplasticity
N-Acetyl Semax Amidate is particularly well-suited for individuals focused on cognitive enhancement through bdnf and ngf-mediated neuroplasticity. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Neuroprotection during and after cerebral ischemic events or brain injury
N-Acetyl Semax Amidate is particularly well-suited for individuals focused on neuroprotection during and after cerebral ischemic events or brain injury. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Nootropic stacking for enhanced learning, memory, and cognitive processing speed
N-Acetyl Semax Amidate is particularly well-suited for individuals focused on nootropic stacking for enhanced learning, memory, and cognitive processing speed. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Attention and focus improvement for cognitively demanding tasks
N-Acetyl Semax Amidate is particularly well-suited for individuals focused on attention and focus improvement for cognitively demanding tasks. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Selank
Anxiety Without the Fog
If traditional anti-anxiety medications leave you feeling sedated, foggy, or 'not yourself,' Selank offers a refreshing alternative. It calms anxious thoughts while keeping your mind sharp—like turning down the volume on worry without muting your brain [1].
Cognitive Performers
Students, professionals, and anyone facing demanding mental tasks love Selank for its dual action. It simultaneously reduces performance anxiety while enhancing memory and focus—the best of both worlds when you need to think clearly under pressure [1][2].
Stress Resilience Seekers
Chronic stress wreaks havoc on your brain. Selank helps protect against stress-induced cognitive decline by supporting BDNF levels and modulating your stress response [2]. Think of it as building a buffer between you and life's daily pressures.
Natural Approach Enthusiasts
Derived from tuftsin—a natural peptide your own immune system produces—Selank appeals to those seeking more 'natural' solutions [4]. It works with your body's existing systems rather than overriding them like synthetic drugs.
Side effects
N-Acetyl Semax Amidate
Common
- Nasal irritation
- Headache
- Mental overstimulation or restlessness
- Sleep difficulty
- Appetite changes
Uncommon
- Hair darkening
Serious
- Allergic reaction
Selank
Common
- Nasal irritation
- Mild fatigue
- Mild headache
- Injection site redness
Uncommon
- Vivid dreams
- Dizziness
Serious
- Allergic reaction
Safety & evidence
N-Acetyl Semax Amidate
Evidence level
Moderate human trials (Phase 1-2)
FDA status
Research compound
Safety overview
N-Acetyl Semax Amidate shows excellent safety tolerability in Russian clinical studies with no serious adverse events reported at therapeutic doses. The amidate modification significantly enhances CNS penetration and metabolic stability compared to parent Semax, reducing dosing frequency. Side effects are primarily mild nasal irritation, transient headaches during initiation, and rare increases in dopaminergic tone manifesting as restlessness or insomnia at high doses, easily managed through dose adjustment.
Contraindications
- Known hypersensitivity to Semax, ACTH fragments, or any formulation component
- Pregnancy and breastfeeding — insufficient safety data in these populations
- Active seizure disorders — neurostimulatory effects may lower seizure threshold in susceptible individuals
- Acute psychotic episodes — dopaminergic and neurostimulatory effects may exacerbate symptoms
Selank
Evidence level
Limited human trials
FDA status
Research compound
Safety overview
The safety record comes from small Russian trials, and the numbers are worth seeing. In the 62-person generalised-anxiety and neurasthenia trial, 30 people took selank at 2,700 mcg a day and 32 took medazepam 30 mg a day for 14 days; the two calmed anxiety about equally, and selank also reduced fatigue where the benzodiazepine did not [9]. A second trial of 60 people with phobic-anxiety and somatoform disorders compared it with phenazepam and reported a clear anxiolytic effect that lasted about a week after the last dose [3]. The registered label lists only two side effects — an unpleasant taste when the drops run from the nose into the throat, and allergic reactions in people sensitive to the ingredients — and records no cases of overdose, which it attributes to how fast the peptide breaks down [7]. Neither trial published a per-arm adverse-event rate, so there is no side-effect percentage to compare against placebo.
Contraindications
- Pregnancy or planning to become pregnant
- Currently breastfeeding
- Known allergy to peptide components
- Children and adolescents
- Severe psychiatric disorders requiring immediate intervention
Which is right for you?
Choose N-Acetyl Semax Amidate if...
- Cognitive enhancement through BDNF and NGF-mediated neuroplasticity
- Neuroprotection during and after cerebral ischemic events or brain injury
- Nootropic stacking for enhanced learning, memory, and cognitive processing speed
- Attention and focus improvement for cognitively demanding tasks
Choose Selank if...
- Anxiety relief without sedation
- Cognitive enhancement and focus
- Memory improvement
- Stress resilience