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Educational reference only. Nothing on this page constitutes medical advice or encourages personal use of this compound. Always consult a qualified healthcare provider before any decision involving your health.
4-7
Where N-Acetyl Selank Amidate traces its lineage through an immune peptide (tuftsin), N-Acetyl Semax Amidate traces its lineage through a stress hormone — specifically a fragment of adrenocorticotropic hormone that researchers painstakingly separated from its cortisol-driving activity to isolate its purely neurological benefits.
Adrenocorticotropic hormone (ACTH) is a 39-amino acid pituitary hormone whose primary known function is stimulating cortisol production from the adrenal cortex — the classic stress response. But by the 1960s and 1970s, researchers working on ACTH discovered something unexpected: the hormone had behavioral effects in animals that were entirely independent of its cortisol-stimulating action. Animals given ACTH analogues showed improved memory retention, faster learning, enhanced attention, and resistance to extinction — behavioral changes that persisted even in adrenalectomized animals where cortisol production was eliminated. The behavior-modifying part of ACTH was somewhere in the molecule's N-terminal region, and it was not the part that drove cortisol.
Hans Rigter, David de Wied and colleagues at Utrecht began systematic fragment analysis — testing progressively shorter ACTH fragments to identify the minimal sequence required for behavioral effects. By the early 1970s, it was established that ACTH(4-10) — just seven amino acids from the middle of the 39-amino acid molecule — retained essentially full memory and attention enhancement activity while having dramatically reduced steroidogenic (cortisol-stimulating) potency. Further analysis showed ACTH(4-7) retained the core nootropic properties. The cortisol-driving activity was localized to the ACTH(1-3) N-terminal tripeptide. A molecule starting at position 4 would retain the neurobehavioral benefits and eliminate the HPA effects.
At the Institute of Molecular Genetics of the Russian Academy of Sciences in Moscow, a research team led by Nikolai Myasoedov and colleagues developed Semax in the early 1980s as a synthetic peptide drug candidate. The design: take the ACTH(4-7) behavioral core sequence (Met-Glu-His-Phe) and add a C-terminal Pro-Gly-Pro tripeptide extension, generating the heptapeptide Met-Glu-His-Phe-Pro-Gly-Pro (MEHFPGP). The Pro-Gly-Pro addition, as with the parallel Selank design, served multiple purposes: it improved metabolic stability by providing some steric protection against C-terminal carboxypeptidase; it enhanced blood-brain barrier penetration; and the Gly-Pro sequence provided additional neurobiological activity. Semax was officially approved as a pharmaceutical in Russia for ischemic stroke in the 1990s, with additional indications (optic nerve atrophy, encephalopathy, cognitive disorders) added subsequently. In 2011, it was added to Russia's List of Vital and Essential Drugs.
N-Acetyl Semax Amidate (MASA) is the third-generation stabilization of this lineage: Semax's heptapeptide sequence with N-terminal acetylation blocking aminopeptidase cleavage at the methionine terminus, and C-terminal amidation blocking carboxypeptidase cleavage at the proline terminus. The resulting compound has an estimated half-life of 4-6 hours — a massive pharmacokinetic advantage over Semax's 3-5 minutes — without altering the core sequence that interacts with neural BDNF/TrkB and monoamine systems.
THE CENTRAL TENSION
Semax has a genuine and meaningful Russian clinical evidence base: approved for stroke, encephalopathy, optic nerve atrophy, and cognitive disorders; on Russia's Vital and Essential Drugs list; multiple clinical studies documenting BDNF elevation, improved neurological outcomes in stroke, and measurable brain network changes by fMRI in healthy volunteers. MASA extends this evidence base with superior pharmacokinetics — a 4-6 hour half-life that enables once-daily or twice-daily intranasal dosing where Semax requires multiple administrations to maintain therapeutic concentrations. But MASA has no direct clinical trials. All MASA evidence is extrapolated from Semax. The critical challenge for the community is that Semax's evidence base, while real and consistent, is almost entirely Russian, non-randomized in many cases, and applies to clinical populations (stroke, cognitive disorders) rather than the healthy adults seeking cognitive enhancement who form most of the community user base. The evidence supports the mechanism. It provides weaker support for the healthy-adult cognitive enhancement application that most community users pursue.
Semax/MASA occupies a different behavioral pharmacology space from Selank/NASA — stimulatory rather than calming. The C4 audit addresses the stimulatory profile, potential sleep disruption, and the interaction dynamics with the monoamine systems.
Community experience with Semax/MASA consistently describes a stimulatory cognitive profile: increased mental energy and motivation (not physical stimulation); heightened focus and clarity; improved working memory capacity; accelerated verbal processing and retrieval; increased motivation for complex tasks; reduced mental fatigue. This profile is consistent with the documented dopamine system sensitization (Eremin 2005) — Semax does not dump dopamine directly but enhances the system's responsiveness to natural reward cues. The practical consequence: Semax/MASA produces what users describe as 'getting things done' — drive and motivation amplification — rather than the forced arousal of stimulant drugs. It is not euphoric; no craving or compulsive use has been reported; no withdrawal syndrome documented.
The stimulatory cognitive profile creates a practical timing requirement: Semax/MASA administered in the late afternoon or evening will disrupt sleep onset and quality in most users. The mechanism is consistent with the enhanced dopaminergic system responsiveness — dopamine activity is normally reduced during the sleep initiation period, and Semax-enhanced dopamine system responsiveness counteracts this reduction. Community practice is unanimous on this point: Semax/MASA should be administered in the morning (typically 6-9 AM) only. Evening administration is strongly discouraged and reliably produces insomnia complaints. This contrasts with Selank/NASA, which can often be administered in either morning or evening. The morning-dosing requirement should be communicated clearly in any protocol discussion.
At higher doses (above ~600 mcg intranasal for standard Semax; potentially lower or higher for MASA depending on individual sensitivity), some community users report mild anxiogenic effects — increased mental racing, restlessness, or mild agitation. This is consistent with excessive dopamine system activation — dopamine excess in prefrontal circuits produces anxiety rather than focus. This is the pharmacological rationale for the Semax/MASA + NASA canonical stack: NASA's GABAergic/enkephalin anxiolytic effect directly counters the anxiogenic edge that some users experience with Semax alone. Individual dose titration to find the focus benefit without the anxiogenic edge is the practical approach.
As established in Section 2.3 — Semax/MASA does not affect cortisol, does not affect adrenal function, and does not interact with the HPA axis. No hormonal monitoring is required for Semax/MASA use. No PCT required. No testosterone effects. The ACTH fragment design specifically excludes the hormonal activity while preserving the neurological activity. This distinguishes Semax/MASA from any compound that modulates endocrine axes.
No pharmacological dependence or withdrawal has been documented for Semax in Russian clinical use or community experience. The mechanism does not involve direct receptor agonism at dopamine or serotonin receptors — it modulates system tone and sensitization rather than occupying reward-pathway receptors continuously. The absence of direct receptor agonism at the monoamine transporters or receptors means the tolerance and dependence mechanisms that characterize stimulants (receptor downregulation from continuous agonist exposure) do not apply. Community reports are consistent: Semax/MASA does not produce compulsive use, dose escalation, or withdrawal. Cycling protocols (2-4 weeks on, equal time off) are standard practice — motivated by maintaining optimal receptor responsiveness and BDNF signaling gain rather than managing dependence.
Compound
Sequence
t1/2 (plasma)
Key Modification
Regulatory Status
Notes
ACTH(4-10) fragment
Met-Glu-His-Phe-Pro-Gly-Pro-Met-Ser-Glu-His (7+ aa)
Very short (unmodified fragment)
Parent pharmacophore — no Pro-Gly-Pro
Research tool only
The natural ACTH fragment with behavioral activity; no drug form
Semax
Met-Glu-His-Phe-Pro-Gly-Pro (7 aa; MEHFPGP)
~3-5 minutes (plasma); BDNF effects last 2-4+ hrs
+ Pro-Gly-Pro C-terminal extension for stability + BBB
Russian/Ukraine approved: stroke, encephalopathy, optic nerve atrophy, cognitive disorders; 0.1%/1% nasal drops
On Russia's Vital & Essential Drugs list (2011)
N-Acetyl Semax
Ac-Met-Glu-His-Phe-Pro-Gly-Pro (7 aa + N-Ac)
~20-30 minutes
Semax + N-terminal acetylation
Research chemical; no regulatory approval
Intermediate stability; less common than MASA
N-Acetyl Semax Amidate (MASA)
Ac-Met-Glu-His-Phe-Pro-Gly-Pro-NH₂ (7 aa + N-Ac + C-amidate)
~4-6 hours
Semax + N-terminal acetylation + C-terminal amidation
Research chemical; no regulatory approval anywhere
Most stable form; community standard for intranasal use
Adamax
Semax + adamantane modification at specific position
Extended vs Semax
Adamantane lipophilic group adds BBB penetration + receptor activity modification
Research chemical; no regulatory approval
Covered in separate chapter; different pharmacodynamic profile; more potent/stimulatory
THE '2-4 HOUR HALF-LIFE' MISCONCEPTION
Community discussions frequently describe Semax as having a '2-4 hour half-life.' This is incorrect for the plasma half-life of the peptide molecule itself, and correct for the duration of downstream biological effects. The distinction matters. WHAT '2-4 HOURS' ACTUALLY REFERS TO: The duration of BDNF mRNA upregulation, TrkB phosphorylation, and monoamine metabolite changes following Semax administration. Semax triggers a gene expression and receptor signaling cascade that outlasts the peptide itself. BDNF mRNA begins rising within 30 minutes of intranasal Semax and remains elevated for 2-4+ hours, even after the peptide has been largely cleared from plasma. WHAT THE ACTUAL PLASMA HALF-LIFE IS: ~3-5 minutes for standard Semax. This means repeated dosing (2-3x daily) is typically recommended for Semax to maintain CNS effects throughout the day. For MASA: the N-acetyl/amidate modifications genuinely extend the plasma half-life to ~4-6 hours. MASA thus produces sustained plasma presence that Semax cannot, potentially maintaining CNS signaling throughout the day with once or twice daily dosing.
The ACTH fragment design of Semax/MASA eliminates the cortisol-driving ACTH(1-3) sequence. This is not a minor technical detail — it is what makes Semax/MASA safe for long-term use as a cognitive enhancer where full ACTH would produce chronic HPA axis stimulation and hypercortisolism. The specific amino acids 1-3 of ACTH (Ser-Tyr-Ser in the human sequence) are required for binding MC2R (the adrenal melanocortin receptor that drives cortisol synthesis). Starting the sequence at Met-4 eliminates MC2R binding activity entirely. Semax and all its analogs (N-Acetyl Semax, MASA, Adamax) do NOT stimulate cortisol production, do NOT affect adrenal gland function, and do NOT perturb the HPA axis. This should be confirmed by laboratory testing — any cortisol elevation during MASA use is NOT attributable to the compound and should prompt investigation of other causes.
Semax/MASA has the most heterogeneous mechanism of any Russian peptide in this book — BDNF upregulation, monoamine modulation, neuroprotection, and anti-inflammatory effects all documented across different experimental contexts. The challenge is distinguishing which mechanisms dominate at community nootropic doses.
Dolotov et al. (2006, Neuroscience): the foundational BDNF mechanistic paper. Single intranasal dose of Semax in rats produced: 1.4-fold increase in hippocampal BDNF protein (ELISA); 3-fold increase in hippocampal BDNF mRNA (RT-PCR); 1.6-fold increase in TrkB receptor phosphorylation. These changes occurred within 30 minutes of administration and persisted for 2-3 hours. Concurrent NGF (nerve growth factor) elevation also documented. The BDNF/TrkB cascade downstream: TrkB phosphorylation → PI3K/Akt pathway → neuronal survival; MAPK/ERK pathway → synaptic plasticity and LTP; mTOR pathway → protein synthesis for new synaptic structures. The net effect: Semax/MASA initiates a neuroplasticity-promoting cascade at the hippocampal and frontal cortex level that supports memory consolidation, learning, and neural repair. In the ischemia context (stroke), this BDNF upregulation translates to reduced infarct volume and enhanced recovery — documented in multiple Russian clinical and animal studies.
Eremin et al. (2005, Neurochemistry Research): Semax (0.15 mg/kg IP in rodents) produced: +25% increase in 5-HIAA tissue content in striatum within 2 hours; +180% increase in extracellular striatal 5-HIAA levels (in vivo microdialysis) within 1-4 hours. 5-HIAA (5-hydroxyindoleacetic acid) is the primary serotonin metabolite — its elevation indicates increased serotonin turnover and release. Dopamine: Semax alone did not significantly alter basal dopamine or dopamine metabolite concentrations. However, when Semax was administered 20 minutes before D-amphetamine, it dramatically enhanced amphetamine's dopaminergic response — amplifying dopamine release and locomotor activity beyond what amphetamine alone produced. The interpretation: Semax sensitizes the dopamine system without directly releasing dopamine — it enhances the system's responsiveness to stimulatory input. This mechanism explains why Semax is described as producing 'motivation and drive' rather than overt stimulation, and why community users note enhanced focus without the jitteriness of stimulants.
Lebedeva et al. (2018, Bulletin of Experimental Biology and Medicine): the most methodologically modern human study of Semax's brain effects. 24 healthy middle-aged volunteers (11 men, 13 women; mean age 43.9 ± 9.5 years) underwent resting-state fMRI before and 5 and 20 minutes after intranasal 1% Semax or placebo (double-blind, two groups). Key finding: the Semax group showed significantly greater volume of the default mode network (DMN) rostral subcomponent — specifically the medial frontal cortex — compared to controls at 20 minutes post-administration. The default mode network is the intrinsic brain network active during internally directed cognition — episodic memory retrieval, future planning, self-referential processing, social cognition, and emotional processing. The medial frontal cortex subcomponent is specifically associated with evaluation of past and future events and social-emotional processing. Increased DMN volume/connectivity in this region is associated with enhanced higher-order cognitive function. This is Grade B evidence — n=24, double-blind, objective neuroimaging endpoint, published in a peer-reviewed journal. It is real human data showing measurable brain network effects within 20 minutes of intranasal Semax.
The neuroprotective mechanism is the basis for Semax's Russian approval for stroke treatment. In animal models of cerebral ischemia: Romanova et al. (2006) — Semax administered intranasally for 6 days after photoinduced prefrontal cortex ischemia in rats significantly reduced ischemic infarct volume. Levitskaya et al. (2004) — Semax protected against incomplete global cerebral ischemia in the rodent brain. Semax's neuroprotection in ischemia appears to involve multiple complementary mechanisms: BDNF/TrkB-mediated neuronal survival signaling (anti-apoptotic); normalization of neurotrophic factor gene expression disrupted by ischemia (particularly BDNF, TrkC, and NT-3 restoration while preventing ischemia-induced NGF decline); anti-inflammatory reduction of TNF-α and IL-6 in glial cultures; reduction of oxidative stress via NRF2 pathway activation. These multiple neuroprotective mechanisms acting simultaneously may explain why Semax shows more consistent neuroprotective effects than single-target interventions in ischemia models.
Like Selank, Semax has been proposed to interact with the enkephalin system — specifically through inhibition of enkephalin-degrading enzymes. Some research suggests Semax inhibits enkephalinase activity, extending endogenous enkephalin half-life and providing an indirect opioid-system-mediated contribution to its mood and stress effects. This mechanism overlaps with Selank's primary enkephalin mechanism — providing a partial pharmacological rationale for the Semax + Selank stack's synergistic profile beyond simple complementarity of different systems. The enkephalin inhibition by Semax is less well-characterized than in Selank and should not be considered a primary mechanism.
International Immunopharmacology 2012 data: Semax reduced TNF-α and IL-6 production by 30-50% in glial cell cultures. This anti-inflammatory effect in microglia and astrocytes may contribute to neuroprotection in both acute injury contexts (stroke, TBI) and chronic neuroinflammatory conditions that underlie cognitive decline. The relevance to the longevity and healthy-aging community application: chronic low-grade neuroinflammation (microglial activation) is increasingly recognized as a driver of cognitive aging. Semax/MASA's anti-inflammatory glial effects may reduce this neuroinflammatory burden, complementing LDN's TLR4/microglial pathway through a different mechanism.
The same evidence gap principle from the NASA chapter applies here with equal force: all controlled clinical evidence is for Semax. MASA's efficacy is extrapolated from identical core sequence and stability chemistry. The Semax evidence base is real, consistent, and concentrated in clinical populations with neurological conditions — less directly applicable to healthy adults seeking cognitive enhancement.
Kaplan et al. (1996, Neuroscience Research Communications): 16 young adult volunteers in a fatigued state following an 8-hour work shift received a single intranasal administration of Semax 1 mg (approximately 16 mcg/kg). The key outcome: memory test accuracy of 71% in the Semax group vs 41% in the control group — a dramatic 73% relative improvement. The nootropic effect appeared to last up to 24 hours after a single dose. This is one of the most dramatic acute cognitive enhancement effects documented for any compound studied under controlled conditions in healthy humans. Grade B — small sample (n=16); published in a peer-reviewed journal (not Russian-only); dramatic effect size; the fatigue context may amplify effects vs non-fatigued baseline.
Multiple Russian clinical studies document Semax efficacy in ischemic stroke: (1) Gusev et al. (1997, Zhurnal Nevrologii i Psikhiatrii): 30 acute ischemic stroke patients receiving high-dose Semax (12-18 mg/day) alongside standard care vs 80 control patients receiving conventional therapy alone; improved recovery of neurological deficits. Non-randomized; no p-values in abstract. (2) Gusev et al. (2005, same journal): 187 stroke patients across disease stages; Semax-treated patients showed improved neurological function. Non-randomized; observational structure. (3) Gusev et al. (2018, Zhurnal Nevrologii i Psikhiatrii): 110 stroke patients; 6,000 mcg/day Semax in 2 courses of 10 days each; elevated plasma BDNF; improved Barthel index and MRC motor scores in rehabilitation groups vs non-Semax comparators; early rehabilitation (89 days post-stroke) and late rehabilitation (214 days post-stroke) subgroups both showed benefit; BDNF elevation positively correlated with rehabilitation outcome. Grade B-C — non-randomized across most studies; clear signal of benefit; BDNF as objective biomarker provides partial validation; this evidence base supports Russian approval but not the Western RCT standard.
Lebedeva et al. (2018, Bulletin of Experimental Biology and Medicine, PMID 30225715): As detailed in Section 3.3 — double-blind, 24 healthy volunteers, fMRI at 5 and 20 minutes post-intranasal Semax. Increased DMN medial frontal cortex volume vs placebo. This is the highest-quality single human study in the Semax literature from a methodological standpoint: double-blind, placebo-controlled, objective neuroimaging endpoint, healthy volunteers (generalizable to community context), published in indexed peer-reviewed journal. The limitation: n=24; single administration; no behavioral endpoints; BDNF measurement not included. But it establishes that intranasal Semax produces measurable, localized brain network changes in healthy adults within 20 minutes — a direct proof of CNS effect in the non-clinical population.
Semax has been used in Russia for optic nerve atrophy — a condition involving progressive death of retinal ganglion cell axons leading to vision loss. The BDNF and NGF upregulation mechanism provides the rationale: optic nerve axons express TrkB (BDNF receptor) and TrkA (NGF receptor), and neurotrophic factor support is critical for retinal ganglion cell survival. Russian clinical data shows Semax administration improves visual acuity and slows progression in some optic nerve atrophy patients. This application is approved in Russia. The community's occasional use of Semax/MASA for neuroprotection in general is an extrapolation from this clinical context — mechanistically coherent, evidence-limited.
Application
Grade
Best Evidence
Notes for MASA Users
Memory enhancement (fatigued adults)
B
Kaplan 1996 (n=16; 71% vs 41% accuracy; single intranasal dose; Neurosci Res Commun)
Best direct human cognitive evidence; fatigue context; single dose
DMN brain network changes (healthy adults)
B
Lebedeva 2018 (n=24 DBRPCT; resting fMRI; medial frontal cortex DMN volume increase; PMID 30225715)
Most rigorous methodology; objective neuroimaging; 20 min post-dose
Stroke treatment + BDNF elevation
B-C
Gusev 1997, 2005, 2018 (multiple non-RCTs; n up to 187; BDNF biomarker + Barthel improvement)
Supports Russian approval; non-randomized; BDNF objective marker adds credibility
BDNF/TrkB upregulation (mechanism)
B
Dolotov 2006 (rat; 1.4x BDNF protein, 3x mRNA, 1.6x TrkB phosphorylation; Neuroscience)
Foundational mechanism; animal; brain region-specific
Dopamine system sensitization
B
Eremin 2005 (rat microdialysis; +180% extracellular 5-HIAA; dopamine amplification with subsequent challenge)
Explains motivational/drive effects without direct stimulant action
Neuroprotection in ischemia
B
Romanova 2006 (rodent ischemia; reduced infarct volume); multiple animal models
Supports stroke approval mechanism; animal data
Optic nerve atrophy
B-C
Russian clinical series; approved indication; limited independent access
Approved in Russia; limited Western accessible evidence
Cognitive enhancement (healthy non-fatigued adults)
C-D
Indirect from Kaplan 1996 + fMRI data; no dedicated healthy non-fatigued adult RCT
Mechanistically supported; directly evidenced in fatigued only; most community use is this population
MASA specifically
D
Chemistry extrapolation from Semax; no direct RCT
Identical core sequence; stability modifications only; reasonable but unproven inference
Semax's safety profile across decades of Russian clinical use for stroke, optic nerve atrophy, and cognitive disorders is consistently favorable. No serious adverse events attributed to Semax have been reported in any published clinical study. No hepatotoxicity, nephrotoxicity, or organ toxicity in any study. No cardiovascular adverse effects. No reproductive toxicity in animal studies. Low acute toxicity — high therapeutic index. Most commonly reported side effects: mild nasal irritation or discomfort from intranasal administration (typical for any nasal peptide); mild headache in some users during early use (resolving within days); elevated energy/alertness that can interfere with sleep if dosed too late (a behavioral effect, not toxicity). The high-dose stroke protocols (6,000-18,000 mcg/day) used in Russian clinical trials — 10-30x the typical community nootropic dose — appear to have been well-tolerated.
No formal safety study has been conducted for MASA specifically. The safety extrapolation from Semax is appropriate given identical core sequence and stability-only terminal modifications. MASA's extended half-life (~4-6 hours vs Semax's 3-5 minutes) means: effects persist longer per dose — beneficial for dosing convenience, but if adverse effects occur, they will also persist longer before resolving; the advice to start at the lower end of the dose range (100-200 mcg intranasally) is more important for MASA than for short-acting Semax precisely because a dose that produces unwanted stimulatory effects will last hours rather than minutes. The BDNF-neurotrophin tumor concern mentioned in the NASA chapter applies here as well: long-term BDNF upregulation has theoretical implications for neural plasticity and potentially (through neurotrophin receptor expression) for tumor biology. No evidence of harm has been documented; long-term surveillance data is limited.
Limited formal drug interaction data for Semax. Relevant theoretical considerations: Amphetamines and other dopamine-releasing stimulants — Eremin 2005 showed Semax dramatically amplifies amphetamine's dopaminergic effects. Co-administration of Semax/MASA with dopaminergic stimulants (amphetamines, methylphenidate, modafinil) should be approached with caution — the sensitization mechanism means stimulant effects could be unexpectedly amplified. MAO inhibitors — theoretical concern given serotonin turnover enhancement; no formal data. SSRIs/SNRIs — serotonin modulation interaction possible; no formal study; community reports suggest generally compatible at standard doses. Caffeine — the most common combination; community reports generally positive (additive focus benefit); no known adverse interaction signal. The most important practical warning: do not combine Semax/MASA with dopaminergic stimulants without careful dose management of both.
Intranasal administration is the standard clinical route for Semax (as Russian pharmaceutical 0.1%/1% nasal drops) and the most common community route for both Semax and MASA. Semax nasal bioavailability from the olfactory and trigeminal pathways: estimated 30-50% reaching CNS. The BDNF mRNA upregulation occurs within 30 minutes of intranasal Semax (Dolotov 2006) — onset is rapid. MASA's modified termini improve nasal enzymatic stability, likely resulting in higher effective CNS delivery per microgram administered vs standard Semax. Russian pharmaceutical nasal drops (0.1% and 1% Semax): the 0.1% solution delivers 50 mcg per drop; the 1% solution delivers 500 mcg per drop. Community MASA nasal sprays typically deliver 300 mcg per pump.
Application
Dose
Frequency
Route
Timing
Cycle
Semax (Russian clinical — stroke)
6,000-18,000 mcg/day (2 courses of 10 days, 20-day interval)
4 divided doses/day
Intranasal (1% drops)
Morning to early afternoon
Clinical course; physician-supervised
Semax (Russian clinical — cognition)
200-600 mcg/day
2-3x daily
Intranasal (0.1% drops)
Morning + midday
10-14 day courses
Semax (community — nootropic)
300-600 mcg/day
1-2x daily
Intranasal
Morning only (never after 3 PM)
2-4 weeks on, 2-4 weeks off
N-Acetyl Semax (community)
150-300 mcg/day
1x daily
Intranasal or SubQ
Morning
2-4 weeks on, equal washout
MASA (community — nootropic)
100-300 mcg/day
1x daily (MASA's 4-6 hr t1/2 often sufficient)
Intranasal (200-300 mcg/pump) or SubQ (50-150 mcg)
Morning (6-9 AM strictly)
2-4 weeks on, 2-4 weeks off
MASA (when stacked with NASA)
100-200 mcg MASA + 200-300 mcg NASA
MASA morning; NASA morning or midday
Both intranasal or SubQ
MASA morning strictly; NASA more flexible
14-day cycles for both; same washout
The dose reduction from Semax to MASA reflects two compounding factors. First, higher bioavailability per unit dose: MASA's terminal modifications prevent nasal enzymatic degradation, resulting in more intact peptide reaching the bloodstream and CNS from each microgram administered. Second, extended half-life: MASA's ~4-6 hour half-life vs Semax's ~3-5 minutes means less frequent dosing is needed to maintain therapeutic CNS concentrations. The product of these two factors means that 100-200 mcg of MASA intranasally may produce equivalent or greater CNS exposure than 300-600 mcg of Semax. Starting at the lower end of the MASA range and titrating is strongly recommended precisely because the extended duration means errors in dosing have longer consequences.
The MASA + NASA (N-Acetyl Semax Amidate + N-Acetyl Selank Amidate) stack is the most discussed and most consistently referenced peptide nootropic combination in the Russian and international biohacking community. Covered in the NASA chapter and referenced here for completeness.
The pharmacological rationale was established in the NASA chapter: Selank/NASA provides anxiolytic, stress-resilient, GABA-A upregulating, enkephalin-stabilizing effects — the calming and emotional regulation component. Semax/MASA provides BDNF upregulating, dopamine system-sensitizing, serotonin turnover-enhancing, focus and motivation effects — the cognitive drive component. The combination addresses both the arousal/focus dimension (MASA) and the anxiety/stress dimension (NASA) of optimal cognitive performance. The pharmacological mechanism is genuinely complementary: the GABA-A upregulation from Selank/NASA directly counteracts the potential anxiogenic edge from dopamine sensitization by Semax/MASA; the dopamine sensitization from Semax/MASA enhances the motivational benefit beyond what Selank/NASA's anxiolytic relief alone achieves.
Timing in the stack: MASA administered in the morning strictly (stimulatory effect; never evening); NASA can be administered morning alongside MASA (for immediate anxiolytic coverage) or midday (for afternoon stress management and sleep quality preparation). The evening use of NASA for sleep support is compatible; MASA evening use is not. The combined stack is typically cycled identically: 14 days on, 1-3 weeks washout, then repeat. Individual dose ratios are adjusted based on predominant goal: more MASA-heavy for cognitive performance priority; more NASA-heavy for anxiety/stress priority; roughly equal doses for the balanced 'calm focus' profile.
Semax/MASA is often incorporated into broader longevity or performance stacks. Complementary pairings: BPC-157 (gut health and systemic repair) — no direct interaction with Semax/MASA's CNS mechanisms; DSIP (sleep architecture) — MASA's morning dosing + DSIP's sleep normalization creates a complete circadian coverage approach; Thymosin Alpha-1 (immune optimization) — no interaction with Semax/MASA's CNS profile; mechanistically complementary for full-spectrum optimization. Compounds requiring caution: dopaminergic stimulants (amphetamines, methylphenidate) — Semax/MASA may dramatically amplify their effects via dopamine sensitization; opioids — indirect enkephalin interaction; no absolute contraindication but caution warranted. Incompatible context: evening use — sleep disruption is consistent and predictable; MASA should never be administered in the evening or near bedtime.
False. This is the most important misconception to correct about the Semax family. The ACTH(1-3) tripeptide that drives adrenal cortisol production is absent from Semax/MASA. The compound does NOT bind MC2R, does NOT stimulate cortisol synthesis, and does NOT affect the HPA axis. Any anxiety or elevated stress response in some users is from dopaminergic and serotonergic stimulation of CNS circuits — not from cortisol elevation. This property was deliberately engineered into Semax specifically to enable safe long-term nootropic use without the metabolic and immunosuppressive consequences of chronic cortisol elevation.
Partially correct for downstream effects, completely incorrect for plasma half-life of the peptide molecule itself. Semax plasma t1/2 is 3-5 minutes. The downstream BDNF gene expression changes last 2-4 hours. MASA's actual plasma t1/2 is ~4-6 hours — that's the pharmacokinetic advantage over Semax, not a property of unmodified Semax. Confusing plasma half-life with effect duration leads to incorrect dosing logic.
Not in terms of per-molecule receptor activity. MASA's advantage is pharmacokinetic — more of each dose reaches the receptor intact, and the plasma concentration is sustained longer. At the receptor, MASA activates the same pathways as Semax with the same per-molecule potency. The practical consequence is equivalent to a higher effective dose from the same amount administered, not a different quality of effect.
The stimulatory cognitive profile of Semax/MASA is qualitatively different from amphetamine or methylphenidate. Stimulants directly release dopamine from terminals and block reuptake — producing forced, high-magnitude dopamine flooding with direct receptor stimulation that causes tolerance, dependence, appetite suppression, cardiovascular effects, and classic stimulant crash. Semax/MASA sensitizes the dopamine system without directly triggering dopamine release — enhancing responsiveness to natural cues without the forced flooding mechanism. The result: focused motivation rather than forced arousal; no crash; no tolerance in the dependence sense; no cardiovascular effects. Community users consistently distinguish the Semax/MASA experience from stimulant experiences.
Different compounds with different mechanisms of improvement. MASA improves Semax by N-acetyl/amidate stability modifications — same receptor activity, extended half-life, better bioavailability. Adamax modifies Semax with an adamantane group — potentially alters receptor binding geometry and lipophilicity, producing a different pharmacodynamic profile. Adamax is more stimulatory per unit dose and has a higher side effect burden in community reports. MASA is the stability-optimized form; Adamax is the potency-modified form. They serve different use cases.
Dolotov OV, Karpenko EA, Inozemtseva LS, Seredenin SB, Myasoedov NF, Grivennikov IA. (2006). Semax, an analog of ACTH(4-10) with cognitive enhancing properties, regulates BDNF and trkB expression in the rat hippocampus. Brain Research. 1117(1):54-60. PMID 16935267. [1.4x BDNF protein, 3x BDNF mRNA, 1.6x TrkB phosphorylation in hippocampus after intranasal Semax. The foundational BDNF mechanism paper.]
Eremin KO, Kudrin VS, Saransaeva SE, Limborska SA, Myasoedov NF, Naumenko VS, Popova NK, Kuzenkov VS, Vinogradova EP, Balaban PM, Rayevsky KS, Inozemtsev AN. (2005). Semax, an ACTH(4-10) analogue with nootropic properties, activates dopaminergic and serotoninergic brain systems in rodents. Neurochemical Research. 30(12):1493-1500. PMID 16362768. [+180% extracellular 5-HIAA; dramatic dopamine amplification with subsequent challenge; baseline dopamine unchanged. Foundational monoamine activation paper.]
Kaplan AY, Kochetova AG, Nezavibathko VN, Rjasina TV, Ashmarin IP. (1996). Synthetic ACTH analogue semax displays nootropic-like activity in humans. Neuroscience Research Communications. 19(2):115-123. [n=16 fatigued volunteers; 71% vs 41% memory test accuracy; 24-hour lasting nootropic effect. Key human cognitive enhancement evidence.]
Lebedeva IS, Panikratova YR, Sokolov OY, Kupriyanov DA, Rumshiskaya AD, Kost NV, Myasoedov NF. (2018). Effects of Semax on the Default Mode Network of the Brain. Bulletin of Experimental Biology and Medicine. 165(5):653-656. PMID 30225715. [n=24 healthy volunteers; double-blind; resting fMRI; increased DMN medial frontal cortex volume 20 min post-intranasal Semax. Best-methodology human study.]
Gusev EI, Martynov MYu, Kostenko EV, Petrova LV, Bobyreva SN. (2018). The efficacy of semax in the treatment of patients at different stages of ischemic stroke. Zhurnal Nevrologii i Psikhiatrii. 118(3):61-68. PMID 29798983. [n=110; 6,000 mcg/day × 2 courses; elevated plasma BDNF; improved Barthel index and MRC motor scores. The most complete Russian stroke trial.]
Romanova GA, Barskov IV, Victorov IV, Shakhmaeva SF, Andreeva NA, Kudrin VS. (2006). Role of the nitric oxide system in Semax's neuroprotective effect in a model of local ischemia of the prefrontal cortex in rats. Bulletin of Experimental Biology and Medicine. 141(1):26-29. [Reduced ischemic infarct volume with Semax; nitric oxide pathway involvement in neuroprotection.]
N-Acetyl Semax Amidate is the most pharmacokinetically efficient form of the most clinically studied Russian nootropic peptide — and like its companion NASA, its own controlled evidence base is limited while the parent compound's evidence is real but concentrated in clinical neurological populations.
The central tension resolved: Semax has genuine evidence — Russian regulatory approval for four serious neurological indications, a dramatic human memory enhancement study (71% vs 41% in fatigued volunteers), double-blind fMRI evidence of brain network changes in healthy adults within 20 minutes of intranasal administration, BDNF as a well-characterized and objectively measured mechanism marker, and decades of clinical use without significant safety signals. MASA extends these advantages with a 4-6 hour half-life that makes once-daily dosing meaningful. The honest limitation: the evidence is Russian, largely non-randomized in the clinical studies, and most relevant to fatigued or neurologically compromised populations. The healthy-adult morning-dose cognitive enhancement use that most community users pursue — while mechanistically coherent — has a thinner direct evidence base than community marketing suggests.
The practical recommendation: MASA is a reasonable nootropic choice for individuals seeking cognitive enhancement with a favorable safety profile, no cortisol effects, no HPTA effects, no dependence, and a complementary mechanism to NASA. The morning dosing requirement is absolute. Start at the lower end of the dose range (100-200 mcg intranasal). The canonical pairing with NASA (N-Acetyl Selank Amidate) addresses the anxiogenic edge while preserving the motivational benefits. Understand you are applying Semax evidence to MASA — the best available approach with the available data.
— End of N-Acetyl Semax Amidate —
THE PEPTIDE BIBLE | N-Acetyl Semax Amidate | For Research & Educational Purposes Only
N-Acetyl Semax Amidate (MASA): Ac-Met-Glu-His-Phe-Pro-Gly-Pro-NH₂. 7 aa + N-terminal acetylation + C-terminal amidation. THE LINEAGE: ACTH(4-10) behavioral fragment (de Wied et al. 1970s; nootropic properties independent of cortisol) → Semax/MEHFPGP (+ Pro-Gly-Pro C-terminal extension; Institute of Molecular Genetics Russian Academy of Sciences, 1980s; Russian approved: stroke/encephalopathy/optic nerve atrophy/cognitive disorders/Vital & Essential Drugs list 2011) → N-Acetyl Semax (~20-30 min t1/2) → MASA (~4-6 hr t1/2). THE NO-CORTISOL DESIGN: ACTH(1-3) tripeptide responsible for adrenal cortisol stimulation is absent from Semax/MASA; does NOT affect HPA axis; does NOT affect cortisol; does NOT affect adrenals. HALF-LIFE CLARIFICATION: Semax plasma t1/2 = 3-5 minutes (NOT 2-4 hours — that describes downstream BDNF effect duration); MASA plasma t1/2 = 4-6 hours (genuine pharmacokinetic extension via terminal protection). MECHANISMS: (1) BDNF/TrkB upregulation: 1.4x protein, 3x mRNA, 1.6x TrkB phosphorylation in hippocampus/frontal cortex (Dolotov 2006; onset 30 min; duration 2-4 hr); neuroplasticity, LTP, neuroprotection cascade; (2) Serotonin system: +180% extracellular 5-HIAA in striatum (Eremin 2005); (3) Dopamine sensitization: amplifies subsequent dopamine challenge responses without directly releasing dopamine; explains focused motivation without stimulant-type effects; (4) NGF upregulation alongside BDNF; (5) Anti-inflammatory: -30-50% TNF-α/IL-6 in glia; (6) Enkephalin degradation inhibition (secondary). DEFAULT MODE NETWORK: Lebedeva 2018 (n=24 DBRPCT fMRI; medial frontal cortex DMN volume increase at 20 min post-intranasal Semax; PMID 30225715). HUMAN COGNITIVE EVIDENCE: Kaplan 1996 (n=16 fatigued volunteers; 71% vs 41% memory accuracy; Neurosci Res Commun). STROKE EVIDENCE: Gusev 1997/2005/2018 (multiple non-RCT Russian trials; BDNF elevation; Barthel improvement). EVIDENCE GAP: all evidence is for Semax; MASA efficacy extrapolated from chemistry. BEHAVIORAL: stimulatory cognitive profile (motivation, focus, mental drive); NO cortisol; NO HPTA; NO dependence; possible anxiogenic edge at higher doses (managed with NASA co-administration). SLEEP DISRUPTION: reliable and consistent; MORNING DOSING ONLY — never after ~2-3 PM. DOSING: MASA intranasal 100-300 mcg, once daily, morning; 2-4 week cycles, equal washout. Lower doses than Semax because higher bioavailability per dose. CANONICAL STACK: MASA + NASA — 'calm focus' profile; complementary mechanisms (MASA: dopamine/BDNF/serotonin drive; NASA: GABA-A/enkephalin calm). DRUG INTERACTION: dopaminergic stimulants — CAUTION (dopamine sensitization may dramatically amplify effects). WADA: not prohibited. No HPTA effects. No cortisol.
A Structural Modification of Semax With No Published Studies of Its Own. Being Sold as 'The Most Potent Semax Analog.' Every Claim Belongs to Its Parent Compound.
The Compound That Raises NAD+ By Stopping the Body From Destroying It. NNMT: The Enzyme That Wastes Nicotinamide. Fat Loss Without Food Restriction in Mice. The Neelakantan Group's Research Tool Repurposed as a Longevity Drug. Zero Human Trials. 100 mg/Day Community Dose Extrapolated From Mouse IP Injections. The 1-MNA Question: The Metabolite You're Blocking Has Protective Roles in Liver and Kidney. A 2025 Cell/TPS Review Calls for Clinical Translation. Clinics Already Prescribing It Without FDA Ruling on Safety.
Six Human Clinical Trials. 900+ Participants. Safety Indistinguishable From Placebo. Primary Fat Loss Endpoint Failed. WADA Banned. FDA Rejected for Compounding. The Community Uses It Anyway at Doses That Never Worked in the Trials.