Reference

Last reviewed: 28 Apr 2026
Sources cited: 8
Residues: 7

Primary structure7 residues · 813.9 Da

01MetMethionine

02GluGlutamate

03HisHistidine

04PhePhenylalanine

05ProProline

06GlyGlycine

07ProProline

Nonpolar Polar Acidic Basic Aromatic Gly/Pro

Semax

Last verified: 2026-04-23

At a glance


Also known as	ACTH(4–10) analogue, MEHFPGP
Class	Synthetic heptapeptide, ACTH fragment analogue, nootropic
Typical route	Intranasal only (drops or spray). Oral/sublingual routes have negligible bioavailability.
Plasma half-life	~1–5 minutes (parent peptide, rapidly metabolised)
Duration of effect	12–24 hours (via downstream BDNF/NGF upregulation and active metabolite Pro-Gly-Pro)
Molecular weight	813.9 Da
Sequence	Met-Glu-His-Phe-Pro-Gly-Pro (7 amino acids)

What it is

Semax is a synthetic heptapeptide developed at Russia’s Institute of Molecular Genetics in the 1980s. It is a modified fragment of adrenocorticotropic hormone (ACTH) — specifically amino acids 4–10 — with the N-terminal stabilised and the C-terminal extended with proline-glycine-proline to resist peptidase degradation.

Unlike most peptides in the biohacker space, Semax is a registered medicine in Russia. It holds clinical approval there for stroke recovery and cognitive dysfunction, and has been used in Russian clinical practice since 1994. Outside Russia — including in the UK, US, and EU — it has no regulatory approval and is sold as a research chemical.

It’s typically used as a nootropic: focus, stress resilience, mental stamina under cognitive load. It’s dosed intranasally because the parent peptide is cleared from plasma in minutes; the nose-to-brain route bypasses that.

Mechanism

Semax works through several overlapping pathways, most documented in rodent models:

BDNF and NGF upregulation. A single intranasal dose upregulates BDNF mRNA in the hippocampus within an hour, with the effect persisting 24 hours or more.1 Nerve Growth Factor (NGF) expression is similarly increased. BDNF is the central mechanism most users care about — it’s implicated in learning, memory, and stress resilience.
Dopaminergic modulation. Microdialysis studies in rats show Semax increases extracellular dopamine in the striatum and nucleus accumbens. The mechanism appears to be enhanced dopamine synthesis via tyrosine hydroxylase upregulation, not reuptake inhibition.2
Serotonergic effects. Less characterised but documented modulation of serotonin turnover.
Enkephalinase inhibition. Semax partially inhibits enzymes that break down endogenous opioid peptides (enkephalins), which is the proposed basis for its mild analgesic effect.
Anti-inflammatory / neuroprotective. Reduction of oxidative stress markers, modulation of microglial activation in injury models.

The recently-identified Pro-Gly-Pro (PGP) tripeptide metabolite appears to be pharmacologically active in its own right — which partially explains how a peptide with a 2-minute plasma half-life can produce effects lasting 12–24 hours.3

Routes of administration

Semax is effectively intranasal-only in practice. Other routes exist mechanically but most are impractical or ineffective, and this is worth understanding rather than assuming it’s a limitation.

Intranasal (drops or spray)


Bioavailability to CNS	High relative to oral — direct nose-to-brain transport via olfactory and trigeminal pathways bypasses plasma entirely
Onset	15–60 minutes subjective effect; BDNF upregulation begins within 1 hour of dosing
Duration	12–24 hours of downstream neurotrophic effect despite ~2-minute plasma half-life
Typical dose (this route)	100–600 mcg per administration, 1–3× daily
Equipment	0.1% solution, calibrated nasal spray or dropper bottle
When this route makes sense	Every use-case. This is how Semax is supposed to be administered.

The default and essentially only viable route. Semax was designed for it. Nose-to-brain transport via olfactory and trigeminal nerves gives direct CNS access without plasma dilution, which is why a peptide with a 2-minute plasma half-life produces 24-hour effects.

Subcutaneous injection


Bioavailability to CNS	Low — the peptide must cross the blood-brain barrier, and plasma clearance is too rapid for meaningful CNS exposure
Onset	Largely ineffective for the intended cognitive indications
Typical dose (this route)	Not recommended; community dosing data essentially absent
When this route makes sense	Rarely. A small number of Russian clinical protocols have used SC delivery for specific peripheral indications, but this is not how Semax is deployed for cognitive/nootropic use.

Technically possible, practically pointless for typical use-cases. If you’re injecting Semax, you’re losing most of what makes it work.

Oral / sublingual


Bioavailability	Negligible. The peptide is broken down rapidly in the GI tract.
Typical dose (this route)	Not recommended
When this route makes sense	Never, for practical purposes.

Semax has no meaningful oral bioavailability. Users sometimes report sublingual use with some subjective effect, but this is likely partial nasal absorption via the nasopharynx rather than actual sublingual delivery. The compound was never developed or studied for this route.

Cross-route comparison

There is no meaningful comparison. Semax is intranasal. If you cannot use intranasal administration (nasal congestion, septal damage, preservative sensitivity to commercial sprays), Semax is likely not the right compound for you — consider alternative nootropic peptides or approaches. The N-Acetyl variants (NAS, NASA) share the same intranasal route.

What the evidence says

Honest summary: stronger clinical evidence than most biohacker peptides — but almost all of it is Russian, older, and untranslated into the Western evidence base.

Russian clinical trials:

Multiple randomised placebo-controlled trials in ischaemic stroke recovery when given within 6–12 hours of onset. Outcomes measured on NIHSS, Barthel Index, modified Rankin Scale — consistent improvement over standard care.4
Studies in high-cognitive-load populations — students during exams, pilots under simulated flight stress, operators doing sustained-attention tasks. Reported improvements in vigilance, working memory, reaction time at 400–1,200 mcg/day.
Registered indications in Russia: stroke recovery, transient ischaemic attacks, cognitive dysfunction, optic nerve conditions.

Western evidence base:

Almost nothing. No large randomised Western trials. The Russian results have not been meaningfully replicated by independent Western research groups.
A handful of English-language mechanism papers (BDNF, dopamine, enkephalinase inhibition) provide the neurochemistry.
A 2025 study identified deubiquitination of mu opioid receptors as a new mechanism, relevant to spinal cord injury.3
A 2025 Alzheimer’s model paper examined effects on amyloid aggregation and neuroinflammation.

Community evidence is extensive but polarised. Many users report clear focus and motivation effects within 15–60 minutes of dosing, often with noticeable improvement in stress tolerance over 1–2 weeks. Others report no effect at all. Non-response is real and not uncommon.

Typical use patterns

Russian clinical protocols and Western nootropic-community practice converge reasonably well on the following. Observations, not recommendations.

Dose:

Standard nootropic use: 250–600 mcg per dose, 1–3 times daily
Microdosing pattern: 100–200 mcg, 1–3 times daily — many users prefer this
Russian clinical (stroke/cognitive): 400–1,200 mcg/day total
Most common preparation is a 0.1% solution, delivering ~250 mcg per spray

Timing:

Morning on waking (most common)
Midday top-up during cognitive work
Avoid late-day dosing — stimulant-like effects can disrupt sleep
Effects typically reported within 15–60 minutes; some users describe a more subtle build-up over 30–90 minutes

Cycle:

Russian clinical use: 5–14 day courses, then discontinued
Community use: anything from sporadic as-needed dosing to continuous 4–8 week cycles
Tolerance is not documented at registered doses across 5–14 day courses; long-term (>30 day) chronic use has not been studied

Stacking:

Commonly paired with Selank (anxiolytic heptapeptide from the same Russian research programme) — Semax for focus, Selank for calm; often dosed together in the morning
Sometimes stacked with cholinergic nootropics (alpha-GPC, CDP-choline) to complement BDNF-driven effects
N-Acetyl Semax (NAS) and N-Acetyl Semax Amidate (NASA) are modified variants with reportedly longer duration; community-dosed at lower mcg ranges but the evidence base for the modifications is thinner than for plain Semax

For sensitive systems

Semax is not primarily a histamine-active peptide — unlike BPC-157, it does not strongly provoke mast cell degranulation through its mechanism. However, there are distinct considerations for sensitive populations.

Start dose. 100–200 mcg once daily in the morning. Half a spray on most commercial 0.1% preparations. Hold for 5–7 days before increasing.

Ramp. If tolerated, increase to 250 mcg once daily, then to twice daily (morning + midday). With Semax in this population, the ramp risk is over-stimulation of an already-dysregulated nervous system, not tissue reactivity.

Expected adjustment profile:

Mild headache in the first few days (small percentage of users; mechanism likely vasoactive)
Mild nasal irritation, dryness, or burning — this is about the route, not the peptide
Anxiety or over-stimulation — the one worth flagging for this population. Semax is stimulating by design; in people with already-activated sympathetic tone (common in POTS, anxiety-prone MCAS, PMDD premenstrually), it can tip into feeling wired, jittery, or panicky. Not dangerous, but unpleasant.
Possible insomnia if dosed too late in the day
Transient glucose elevation reported in ~7% of diabetic patients — relevant for anyone tracking blood sugar

What’s not normal and warrants stopping: sustained heart rate elevation, panic attacks, worsening of baseline anxiety, significant sleep disruption that doesn’t resolve with earlier dosing.

What to have on hand:

A way to measure resting heart rate and HRV (your wearable of choice)
Anxiolytic backup if you’re a known responder to the over-stimulation profile — Selank is the peptide-native answer; magnesium glycinate and L-theanine are gentler options
If you have PMDD: be aware that sensitivity can shift across the cycle. Luteal-phase doses may feel different from follicular.

Stop criteria. Stop if over-stimulation doesn’t resolve with dose reduction, if sleep is compromised for more than 3–4 nights, or if any new anxiety symptom emerges that doesn’t fit your baseline.

Interactions worth considering in sensitive populations:

SSRIs/SNRIs: no documented interaction, but both modulate monoamine systems. Semax’s dopamine and serotonin effects may feel amplified in medicated users.
Stimulant ADHD medication (methylphenidate, lisdexamfetamine): stacking with Semax has an additive stimulating effect. Many biohackers do this intentionally; sensitive users should not.
Beta-blockers for POTS: no direct interaction, but Semax’s sympathetic-leaning effects may partly counter the medication’s purpose.
Low Dose Naltrexone (LDN): commonly used in MCAS/autoimmune populations. No documented interaction; Semax’s opioid-receptor-adjacent mechanism (enkephalinase inhibition, mu-receptor deubiquitination) means mechanistic overlap but no reported clinical issue.

Reasonable expectations

Onset. Acute effects (focus, motivation, mental clarity) typically reported within 15–60 minutes of dosing. Peak effect around 1–2 hours, noticeable for 4–8 hours. Some users describe a cumulative effect building over 3–7 days of consistent dosing.

Response rate. Polarised. Community reports suggest roughly two-thirds of users notice a clear acute effect; the remaining third report nothing obvious. Non-response is not failure — it’s a real feature of Semax’s pharmacology that doesn’t reach everyone.

What the literature actually supports.

Stroke recovery (Russian clinical data): reasonable evidence, not independently replicated Westward.
Cognitive performance under load (Russian studies in students, pilots, operators): reasonable evidence, small effect sizes, short durations studied.
BDNF upregulation (rodent mechanism): well-established.
Antidepressant-like effects (rodent stress models, 2024 Inozemtseva et al.): interesting, preclinical only.

What not to expect.

A stimulant hit. Semax is subtler than caffeine or modafinil. People expecting Adderall-style sharpness often report “nothing.”
A cure for ADHD. BDNF modulation and mild dopaminergic effects are not equivalent to stimulant medication.
Long-term cognitive enhancement that persists off-cycle. Current data suggests effects are largely during-use, tapering off over days after discontinuation.
Mood antidepressant replacement. The antidepressant-like signal is rodent-only.
Hair loss — some Reddit reports describe thinning or shedding. There is no clinical data supporting this correlation. Flag for awareness; don’t treat as documented.

Cost

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


0.1% nasal drops / spray (3 mL bottle, ~10–12 mg total)	£25–45
N-Acetyl Semax Amidate (NASA) 0.1% spray	£30–55 (higher for modified variants)
Cost per month, community-standard (500 mcg/day)	~£15–25
Cost per month, sensitive-start (100 mcg/day)	~£5–10
Cost per cycle (14 days, 600 mcg/day)	~£15

Nasal preparations typically last 4–8 weeks depending on dose. Refrigeration extends shelf life; room temperature is acceptable for shorter cycles.

Reconstitution

Semax is almost always supplied pre-made as a 0.1% nasal solution. User-reconstitution from lyophilised powder is possible but uncommon — and because the dose is measured per spray rather than per injection, the calculation is different from injectable peptides.

Standard preparation, 1 mg (1,000 mcg) lyophilised Semax:

Dissolve in 1 mL of saline or sterile water → 0.1% solution (1 mg/mL)
A calibrated nasal spray delivers ~100 µL per actuation = ~100 mcg per spray
For 250 mcg doses: 2.5 sprays (usually rounded to 2 or 3)

Standard preparation, 5 mg lyophilised Semax:

Dissolve in 5 mL → 0.1% solution
Same per-spray calculation

Open the Vial Plan calculator

Commercial nasal spray pumps vary — some deliver 50 µL, some 100 µL, some 140 µL. Measure your pump before trusting the dose. One drop from a pipette is roughly 50 µL; 2 drops per nostril delivers ~100 mcg of 0.1% solution.

Areas of concern ⚠

Safety signals

No large-scale Western clinical trials. Russian registration provides more safety data than most biohacker peptides have, but the dossier is not publicly accessible in English.
Long-term safety (>30 day continuous use) is uncharacterised in peer-reviewed literature. Russian use tends to be in courses, not continuously.
No documented dependence or withdrawal. This is genuinely reassuring — unusual for a compound that affects dopamine.

Over-stimulation in sensitive or anxious individuals

The most commonly reported negative effect. Semax is subtly activating; in the wrong system it amplifies existing sympathetic tone.
More prone to this: pre-existing generalised anxiety, POTS, caffeine-sensitive individuals, anyone in a stress state
Addressable by lower dose, morning-only dosing, pairing with Selank

Nasal route-specific issues

Nasal irritation, burning, dryness — most common side effect overall. Usually mild; saline rinse before or after dosing helps.
Septal irritation with chronic use — not well documented in Semax specifically, but a general concern with daily nasal peptide use. Alternating nostrils and avoiding dosing when the nasal passage is already inflamed is sensible.
Preservatives in commercial sprays (benzalkonium chloride, phenoxyethanol) can provoke reactions in sensitive individuals — unpreserved or custom preparations exist but are harder to source.

Sleep disruption

Dosing too late in the day is a common self-inflicted wound. Avoid anything after ~2 PM for most users, earlier for slow metabolisers.

Diabetic glucose concern

~7.4% of diabetic patients showed mild transient glucose elevation in clinical observation.5 Worth knowing if you’re tracking blood sugar or have pre-diabetes.

Quality and sourcing

Semax is produced by research-chemical suppliers and a small number of Russian pharmacies. Commercial Russian-origin product is generally considered higher quality than Western research-chemical reconstitutions.
Counterfeit product exists — particularly dilute or incorrectly-labelled sprays. Independent third-party testing is rare.
Storage: lyophilised Semax is stable at room temperature for months; reconstituted 0.1% solution should be refrigerated and used within 30–45 days.

Populations where caution is warranted

Pregnancy and breastfeeding — no human data, default contraindication
Uncontrolled hypertension — theoretical based on sympathetic activation
Anxiety disorders — not a contraindication but a reason to start very low
Active psychosis or bipolar mania — mechanistic concern given dopaminergic activity; avoid during active episodes
Under 18 — studied in paediatric populations in Russia for cognitive indications, but not a compound with a clear evidence base for unsupervised use in this age group

Hair loss reports

Reddit reports exist. No clinical data supports or refutes them. Mechanistically plausible (ACTH-fragment analogues can theoretically affect hair cycling) but unconfirmed.

FDA / regulatory status

Jurisdiction	Status	Last verified
US (FDA)	Not approved. Was nominated for 503A consideration but not currently on any active 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 stroke recovery, TIA, cognitive dysfunction, optic nerve conditions. Prescription drug.	2026-04-23
WADA (sport)	Not explicitly listed; would likely fall under “peptides and hormones” prohibitions for tested athletes. Treat as prohibited.	2026-04-23

Narrative. Semax’s regulatory status is unusually asymmetric. It’s a regulated medicine in Russia, a research chemical in most of the rest of the world. There is no active UK or EU regulatory process to license it. The US FDA has not indicated intent to reclassify it. This is unlikely to change.

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

What to track in Peptrax

Semax is a daily-use cognitive compound where the question is whether the subjective effect on focus, output, or mood is real, durable, and worth the cost. The most useful log is short and same-time daily: a focus rating, a brief mood read, a note on output (deep-work hours, words written, problems solved — whatever your work actually is). One week is not enough; four weeks of consistent daily logging is where the pattern emerges, especially against weekends, weather, sleep debt, and the other variables that move the needle for everyone.

Cycle structure is the second signal. Many users cycle Semax 2–4 weeks on, 1–2 weeks off, and the on/off contrast is more informative than the absolute level — if you can’t tell the difference between a Semax week and a clean week, that is the answer. Logging cycle dates and intranasal vs subcutaneous route makes that comparison possible.

For sensitive-systems users, Semax is generally well tolerated but the relevant tracking is whether anxiety-adjacent symptoms (rumination, sleep latency, irritability) get better, worse, or unchanged. The compound is sold as cognitive but it touches mood pathways, and the response is bimodal — some people find it grounding, others activating. Daily mood and sleep notes catch that early.

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