Semax (nasal spray)

Semax is a synthetic heptapeptide analogue of ACTH(4-10) with a C-terminal Pro-Gly-Pro extension that resists peptidase cleavage and improves blood-brain barrier penetration. Developed in 1982 at the Institute of Molecular Genetics, it has been a Russian prescription drug for over three decades, listed among Vital and Essential Drugs since 2011, with indications in ischaemic stroke, traumatic brain injury, cognitive decline, and optic nerve disease. It is not FDA approved, is sold as a research chemical, and as of early 2026 is not on the FDA Category 2 restricted list.

Because only the 4-10 fragment is retained, the melanocortin-driven adrenocortical action of ACTH is absent: Semax does not alter cortisol or other hormonal axes.

Intranasal delivery bypasses the gastrointestinal tract and first-pass hepatic metabolism entirely, and gives access to the nose-to-brain pathways along the olfactory and trigeminal nerves, which is the usual rationale for choosing this route with neuroactive peptides. Onset is roughly 15–30 minutes, peak effect around 90 minutes, and duration 20 to 24 hours per dose, considerably faster in onset than the subcutaneous route.

Dosing is expressed per spray rather than per drawn volume. Pre-filled atomizers commonly dispense 100 mcg per actuation; a 10 mg vial reconstituted in 1 mL of sterile saline yields 200 mcg per 0.1 mL spray and 50 sprays per vial. Titration is therefore stepwise in 100 or 200 mcg increments and there is no reconstitution arithmetic beyond the initial preparation. Oral dosing is not viable owing to gastric peptide degradation.

The primary mechanism is upregulation of brain-derived neurotrophic factor (BDNF). In the rat hippocampus a single intranasal dose increases BDNF protein approximately 1.4 fold, BDNF gene expression approximately three fold, and activation of its receptor TrkB by 1.6 fold (Dolotov et al., 2006). Effects begin within about 20 minutes, peak at roughly 90 minutes, and persist 20 to 24 hours. Downstream consequences are neuronal survival, synaptogenesis, and enhanced synaptic plasticity, which underpins the original indication in post-stroke rewiring.

Monoaminergic modulation is the second axis. Semax does not directly spike dopamine or noradrenaline; it potentiates evoked dopamine release. A 1995 Institute of Molecular Genetics study showed markedly greater dopamine release when Semax was given 20 minutes before amphetamine than with amphetamine alone, and Eremin et al. (2005) confirmed activation of dopaminergic and serotoninergic systems in rodents, including increased serotonin turnover. This accounts for the reported potentiation of caffeine and for the anxiolytic-to-anxiogenic dose dependence.

Neuroprotection is mediated through reduced pro-inflammatory cytokines, antioxidant activity, and increased nerve growth factor (NGF). In ischaemic rat models Semax increased proliferation of endothelial, neuroglial, and progenitor cells. Genome-wide transcriptional analysis (Medvedeva et al., 2014) showed modulation of over 1,500 genes, upregulating immune and vascular genes while suppressing inflammatory ones. Resting-state fMRI shows increased activity and connectivity in the default mode network within minutes of administration.

Additional documented actions include inhibition of enkephalin-degrading enzymes, prolonging endogenous regulatory peptide signalling. The intranasal route changes kinetics, not pharmacology: rapid nose-to-brain delivery with no first-pass loss.

Pharmacologically identical to the injectable: BDNF and NGF upregulation with downstream synaptogenesis and neuroplasticity, potentiation of dopaminergic and serotoninergic transmission, anti-inflammatory and antioxidant neuroprotection, broad transcriptional modulation, and inhibition of enkephalin-degrading enzymes that prolongs endogenous regulatory peptide signalling.

Documented effects: a 2007 study in healthy men under cognitive fatigue found 71% accuracy on memory testing after a single 1 mg intranasal dose versus 41% in controls, lasting up to 24 hours; a 31% improvement in correct responses versus control is also reported. Gusev et al. (2018) treated 110 ischaemic stroke patients with 6,000 mcg/day intranasally for 10 days, a 20 day break, and a second 10 day course, with sustained plasma BDNF elevation and improved motor performance and Barthel index scores. A 2001 study of 30 acute-phase stroke patients showed accelerated neurological recovery, particularly motor. Russian clinical data report 70 to 80% therapeutic efficacy in vascular, inflammatory, and toxic optic neuropathies. Preclinical work shows anxiolytic and antidepressant activity, normalisation of the chronic stress response, and increased resting-state default mode network connectivity, while a 1996 study identified an anxiogenic component at certain doses.

Further reported applications include ADHD, support during opioid and alcohol withdrawal, improvement in non-proliferative diabetic neuropathy, and analgesia consistent with enkephalinase inhibition.

The route changes kinetics, not pharmacology: 15–30 minute onset supports acute, as-needed use and once or twice daily dosing, whereas the subcutaneous route is a once-daily accumulating schedule.

Onset is roughly 20 minutes, peak effect at about 90 minutes, and duration 20 to 24 hours per dose, tracking the BDNF and TrkB time course seen in rodents.

In practice, the first few days bring subtle gains in focus, verbal fluency, and mental clarity, often described as a clean cognitive lift without stimulant jitteriness. Increased interest and engagement without a sense of stimulation is common, as is enhanced responsiveness to caffeine, consistent with dopamine potentiation rather than direct release.

Over 1 to 2 weeks of consistent dosing the cognitive effects consolidate: memory, learning rate, and problem solving become more noticeable, with some users reporting an inflection around days 5 to 7. Some report enhanced creative thinking and visual processing, in line with the default mode network findings.

Effect size scales with baseline deficit. In a well-rested, metabolically healthy individual the change is a refinement; under chronic stress, inflammation, or neurological injury the effect is typically more pronounced. Semax does not compensate for sleep restriction or poor nutrition.

Route-specific observations include nasal irritation or dryness and usually temporary discolouration of the nasal cavity. Late-day dosing can produce light sleep or insomnia. Anxiety response is dose dependent, with anxiogenic effects more likely at higher doses and in anxiety-prone individuals, so titration from the low end is warranted.

Preparation: 10 mg vial reconstituted with 1 mL sterile saline (not bacteriostatic water for nasal use) gives 200 mcg per 0.1 mL actuation and 50 sprays per vial. Pre-filled atomizers commonly dispense 100 mcg per actuation; confirm the per-spray concentration before titrating.

Standard intranasal protocol: 200 to 600 mcg per day, once or twice daily, morning or early afternoon, avoiding late-day dosing owing to dopaminergic activation and sleep disruption. Per-goal tiers: cognitive support 200 to 400 mcg daily; neuroprotection 400 to 600 mcg daily; post-injury recovery 600 mcg daily, noting that Gusev et al. (2018) used 6,000 mcg/day in two 10 day courses separated by 20 days. These practical ranges are not derived from published dose-finding studies; no such studies exist for daily cognitive use.

Split every dose between both nostrils to increase mucosal surface area, reduce pharyngeal runoff, and compensate for the nasal cycle. Fasted state is unnecessary, though clear nasal passages improve absorption.

Cycle: 10 to 14 days on, 2 to 4 weeks off, repeated as needed. Continuous stimulation of BDNF pathways produces adaptation and diminishing returns. Earlier guidance ran 4–6 weeks on with a 2–4 week washout, at 2–5 sprays (200–500 mcg) per dose 1–3 times daily, with a maximum of 5–10 sprays (500 mcg – 1 mg) per dose; a person on 5 sprays three times daily is taking 1.5 mg in a day. Those schedules sit well above the current standard and should be regarded as ceilings. The dose-dependent anxiogenic component (1996) argues for titrating from the low end, particularly in anxiety-prone individuals. N-Acetyl Semax Amidate is reported as more potent and may need lower doses.

Reading note on the schedule below: the listed dose is a daily total, taken as one or two administrations. Refrigerate the prepared atomizer after use.

The human evidence base is entirely Russian, with sample sizes below what Western regulators would require, and no published Western clinical trials exist as of early 2026. Long term safety is therefore not established to Western standards, although more than 30 years of clinical use has not revealed significant safety signals.

Stroke recovery. Gusev (2018) treated 110 ischaemic stroke patients with 6,000 mcg per day intranasally for 10 days, a 20 day break, then a second 10 day course. Plasma BDNF rose and remained elevated throughout; motor performance improved on standardised testing and functional independence improved on the Barthel index. A 2001 study of 30 acute-phase patients showed accelerated return of neurological function, particularly motor function.

Cognition. A 2007 study of healthy men performing cognitive tasks under fatigue found 71% accuracy on memory testing after a single 1 mg intranasal dose versus 41% in controls, a 31% difference, persisting up to 24 hours.

Optic nerve disease. Russian clinical data report 70 to 80% therapeutic efficacy in vascular, inflammatory, and toxic optic neuropathies, with gains in visual acuity, visual field, and colour vision.

Preclinical mechanism. Dolotov et al. (Brain Research, 2006) demonstrated a 1.4 fold increase in hippocampal BDNF protein, approximately three fold increase in BDNF gene expression, and a 1.6 fold increase in TrkB activation after intranasal Semax in rats, with improved learning and memory performance. Medvedeva et al. (BMC Genomics, 2014) showed modulation of over 1,500 genes in rat focal ischaemia, enhancing immune and vascular genes while suppressing inflammatory genes. Eremin et al. (Neurochemical Research, 2005) showed activation of dopaminergic and serotoninergic systems, with dopamine release potentiated rather than directly triggered; a 1995 Institute of Molecular Genetics study found Semax given 20 minutes before amphetamine markedly amplified dopamine release. Stavchansky et al. (2011) and Glazova et al. (2009) extend the ischaemia findings to cell proliferation and neurotrophin transcription. Resting state fMRI shows increased default mode network activity and connectivity within minutes of administration.

Safety. Multiple clinical studies report no significant adverse effects, no hormonal disruption, and no dependency or withdrawal. The 110-patient study at 6,000 mcg per day reported no major adverse events. No published dose finding studies support the daily cognitive protocols used outside clinical settings.