Semax 10mg Review

Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro (MEHFPGP), rationally designed as a metabolically stabilized analog of the adrenocorticotropic hormone (ACTH) fragment 4-10. Developed in the late Soviet and early post-Soviet period at the Institute of Molecular Genetics of the Russian Academy of Sciences, it has accumulated a substantial body of preclinical and some clinical literature focused on neuroprotection, cognitive enhancement, and ischemic stroke recovery. Most of that literature originates from Russian-language journals, which creates both a citation challenge and a legitimate source of underappreciated mechanistic data.

For research purposes, Semax represents an interesting pharmacological probe. It sits at the intersection of melanocortin receptor biology, brain-derived neurotrophic factor (BDNF) regulation, and intranasal peptide delivery - three areas that remain active targets in neuroscience. The 10 mg vial offered through Apollo Peptide Sciences is the most common laboratory quantity, suitable for multiple reconstituted research preparations within a single project.

This review covers the chemistry, proposed mechanisms, published study findings, pharmacokinetics, purity verification, reconstitution considerations, and comparator landscape in full. Every mechanistic and efficacy claim is tied to a numbered citation so that researchers can locate the primary source directly.

Editor's Verdict

The $60.00 price for 10 mg is competitive within the research peptide category. Apollo Peptide Sciences provides batch-specific certificates of analysis (CoA) with HPLC and mass spectrometry data, which is the baseline standard this site requires for a recommended vendor listing.

Specifications

What It Is: Chemistry, Origin, and Sequence Detail

Rational Design from ACTH Biology

The story of Semax begins with a broader research program in the 1970s and 1980s investigating whether short fragments of pituitary hormones could exert central nervous system effects independently of their classical endocrine roles. ACTH itself is a 39-amino acid polypeptide produced by the anterior pituitary, but internal fragments of ACTH had been shown by De Wied and colleagues to influence learning and memory in rodent models without triggering adrenal cortisol release. ^[1] The fragment ACTH(4-10), carrying the sequence Met-Glu-His-Phe-Trp-Gly-Lys, became a benchmark in this literature because it retained behavioral activity while being stripped of the N-terminal sequence required for steroidogenesis.

Soviet researchers at the Institute of Molecular Genetics sought to create a more metabolically stable analog that could survive intranasal administration, the preferred non-invasive route for CNS peptide delivery, long enough to reach target tissues in the brain. The solution was to replace the C-terminal Trp-Gly-Lys of ACTH(4-10) with a Pro-Gly-Pro tripeptide, producing the heptapeptide MEHFPGP. ^[2] Proline residues in peptide sequences introduce conformational rigidity, resist cleavage by most endopeptidases and exopeptidases because proline is not a substrate for many common protease families, and have been documented in other neuropeptide contexts to modulate transport across mucosal membranes. The resulting compound, named Semax, was patented and later registered as a pharmaceutical in Russia for the treatment of stroke, transient ischemic attack, and cognitive impairment, where it is administered as an intranasal solution.

Primary Sequence and Physicochemical Profile

Semax is a linear heptapeptide composed exclusively of L-configured amino acids. Its sequence is:

H2N-Met-Glu-His-Phe-Pro-Gly-Pro-COOH

No D-amino acids, backbone N-methylations, or cyclizations are present in the classical Semax molecule. This distinguishes it from some later synthetic neuropeptide analogs designed to push stability even further. The molecular weight calculates to approximately 813.9 Da from standard average residue masses plus the terminal water molecule, placing Semax firmly in the short neuropeptide range where passive paracellular transport is limited but peptide transporter-mediated uptake remains feasible. ^[3]

The net charge at physiological pH (7.4) is influenced by the glutamate side chain (pKa ~4.1, carrying one negative charge), the histidine side chain (pKa ~6.0, close to neutral at pH 7.4), and the free N-terminus. The overall charge is close to zero at physiological pH, which is favorable for membrane interactions and consistent with the moderate lipophilicity observed empirically. Water solubility is high, consistent with formulation in saline for intranasal use at concentrations of 0.1-1.0% (1-10 mg/mL).

The Pro-Gly-Pro Motif and Stability Engineering

The C-terminal Pro-Gly-Pro sequence deserves specific discussion because it is more than a stability add-on. Pro-Gly-Pro tripeptides appear as functional units in extracellular matrix-derived peptides, particularly as collagen-turnover products, where they have been shown to have independent biological activity including interactions with CXCR2 chemokine receptors and influence on neutrophil chemotaxis. ^[4] Whether this motif contributes to Semax's CNS activity or is purely structural remains an open question, but it provides an additional mechanistic hypothesis that has not been fully excluded in the literature. From a purely synthetic standpoint, the motif effectively blocks C-terminal aminopeptidase attack and substantially reduces the rate of proteolytic cleavage in nasal mucosal tissue and plasma compared with the parent ACTH(4-7) tetrapeptide.

Synthesis and Commercial Preparation

Research-grade Semax is produced by solid-phase peptide synthesis (SPPS) using Fmoc or Boc chemistry, with purification by preparative reversed-phase HPLC to achieve the greater-than-98% purity standard expected of research peptides. The acetate salt form is most common in commercial preparations, though trifluoroacetate salts are also seen depending on the purification buffer system used. Trifluoroacetate has mild cytotoxic potential at high concentrations and is worth noting on a CoA. The lyophilized powder is typically a white to off-white amorphous solid, freely soluble in water and saline.

Mechanism of Action

Understanding how Semax produces its observed effects requires examining several partially overlapping signaling systems. No single receptor with a clean binding affinity constant has been definitively identified for Semax in the way that, for example, naloxone is characterized at mu-opioid receptors. Instead, the compound appears to act through a combination of melanocortin receptor engagement, neurotrophin gene regulation, monoaminergic modulation, and antioxidant effects.

Melanocortin Receptor Engagement

The ACTH(4-7) core of Semax carries the minimal sequence required for engagement of melanocortin receptors, a family of five G protein-coupled receptors (MC1R-MC5R) that bind ACTH, alpha-MSH, and related peptides. Brain melanocortin receptors, particularly MC4R and MC3R, are expressed in hypothalamic, limbic, and cortical regions relevant to cognition and stress responses. ^[5] Several studies have investigated whether the cognitive and neuroprotective effects of ACTH-related fragments are mediated through these receptors.

The evidence here is indirect but consistent. Competitive binding assays show that Semax and related ACTH(4-7) analogs displace radiolabeled melanocortin ligands from MC4R with Ki values in the micromolar range - weaker than alpha-MSH but sufficient to produce receptor-mediated effects at the concentrations achieved in brain tissue after intranasal administration. ^[5] MC4R signaling in the hypothalamus and limbic system couples to Gs proteins, elevating cyclic AMP (cAMP), which activates protein kinase A (PKA) and downstream cAMP-response element binding protein (CREB) phosphorylation. CREB is a transcription factor with well-established roles in synaptic plasticity and memory consolidation, providing a plausible molecular bridge between receptor activation and the behavioral outcomes reported in animal models. ^[6]

Importantly, Semax lacks the ACTH(1-3) sequence responsible for high-affinity MC2R (ACTH receptor) binding on adrenal cells, which explains the observed absence of glucocorticoid-stimulating effects in rodent and human studies. ^[2] This selectivity profile is part of what made Semax attractive as a research tool: it allows investigation of central melanocortin biology without the confounding systemic endocrine effects of full ACTH.

BDNF and Neurotrophin Regulation

Perhaps the most-cited mechanism in the recent Semax literature is the upregulation of brain-derived neurotrophic factor (BDNF) and related neurotrophins. BDNF acts through TrkB (tropomyosin receptor kinase B) receptors and is critical for neuronal survival, synaptic plasticity, long-term potentiation (LTP), and adult neurogenesis. ^[7] Dysregulation of BDNF signaling is implicated in depression, Alzheimer's disease, and post-ischemic neuronal death.

Dolotov and colleagues published a study examining the effect of Semax on BDNF and its high-affinity receptor mRNA in rat frontal cortex following intranasal administration. ^[7] Using quantitative RT-PCR, they found statistically significant increases in BDNF mRNA within 1 hour of Semax administration, with the effect sustained for at least 3 hours at the doses tested in rats. The authors also noted parallel increases in TrkB mRNA, suggesting a coordinated upregulation of both ligand and receptor that could amplify the signal beyond what an increase in BDNF alone would produce. The study did not, however, directly measure BDNF protein levels in synaptic terminals or characterize the upstream transcriptional mechanism responsible for the mRNA increase. Whether this induction is a direct transcriptional effect of melanocortin receptor-CREB activation or an indirect consequence of other signaling events (for example, serotonergic or dopaminergic effects on BDNF promoters) remains incompletely resolved.

A related investigation by the same group examined whether the BDNF induction extended to the spinal cord and subcortical structures or was cortically restricted. The findings suggested a degree of anatomical specificity, with frontal cortex and hippocampus showing the largest increases, which is anatomically coherent with the cognitive effects described in behavioral studies. ^[7]

Serotonergic and Dopaminergic Modulation

Multiple neurochemical studies in rats have reported that Semax administration alters concentrations of monoamine neurotransmitters and their metabolites in specific brain regions. Increased dopamine turnover in the striatum and prefrontal cortex, increased serotonin (5-HT) content in the hippocampus, and modulation of noradrenaline levels in limbic regions have all been reported. ^[8] These effects are relevant because monoaminergic systems are central to attention, working memory, and emotional regulation - precisely the domains where Semax shows behavioral effects in rodent models.

The mechanism by which a heptapeptide influences monoamine metabolism is not trivial to explain. One proposed pathway involves indirect effects through the BDNF-TrkB axis: BDNF is known to modulate the expression of dopamine and serotonin transporters and biosynthetic enzymes, so an upstream BDNF increase could cascade into altered monoamine homeostasis. Another hypothesis involves direct effects of the ACTH(4-7) fragment on melanocortin receptors that sit on monoaminergic neurons or their terminals in the striatum and limbic system. Direct measurement of receptor co-localization and pharmacological blockade experiments needed to distinguish these pathways have not been published in accessible, indexed literature to date.

Antioxidant and Anti-inflammatory Effects

In stroke and ischemia models, Semax has been shown to reduce markers of oxidative stress, including malondialdehyde (MDA) and protein carbonyl levels, in brain tissue following middle cerebral artery occlusion in rats. ^[9] Parallel reductions in pro-inflammatory cytokines (IL-1beta, TNF-alpha) have been reported in the same models. These effects are potentially mediated through melanocortin receptor-dependent suppression of NF-kB signaling, a pathway through which MC4R and MC3R agonists are known to exert anti-inflammatory effects in the periphery, and which has been less thoroughly characterized in the CNS context.

The antioxidant findings are mechanistically interesting because they suggest that Semax's neuroprotective effects in ischemia may be at least partly independent of the neurotrophic mechanisms, providing two partially orthogonal avenues for tissue protection. Whether the antioxidant effects are seen at the same doses and time points as the BDNF induction has not been systematically compared, which represents a gap in the mechanistic literature.

Tissue Distribution and CNS Penetration

Intranasal administration of peptides can achieve CNS delivery through the olfactory and trigeminal nerve pathways, bypassing the blood-brain barrier entirely. For Semax, autoradiographic studies in rats using radiolabeled peptide demonstrated detectable brain radioactivity within 30 minutes of intranasal dosing, with highest concentrations in the olfactory bulb and frontal cortex and lower but detectable levels in hippocampus, striatum, and brainstem. ^[3] Systemic absorption via nasal mucosal vasculature also occurs and may contribute to CNS levels through transcytosis across the blood-brain barrier or through circumventricular organs lacking a tight endothelial barrier.

The absolute bioavailability and CNS penetration fraction in primates or humans has not been established by any published pharmacokinetic study that this review could identify in PubMed-indexed literature. This is a significant gap that limits translation of rodent dose-response data to any research context involving higher mammals.

What the Research Says

Study 1: Semax in Acute Ischemic Stroke (Gusev et al.)

One of the most frequently cited clinical investigations is a controlled trial by Gusev and colleagues examining intranasal Semax in patients with acute ischemic stroke. ^[10] The trial enrolled 60 patients with confirmed ischemic stroke within 6 hours of onset. Patients were randomized to receive either standard therapy plus intranasal Semax (administered as a nasal solution) or standard therapy alone over a 10-day treatment course. The primary endpoints included neurological deficit scoring using standardized Russian neurological scales, activities of daily living scores, and biomarkers of oxidative stress in serum.

The Semax group showed statistically significant reductions in neurological deficit scores compared with controls at day 10, with the authors reporting a mean score improvement approximately 30% greater in the treated group. Oxidative stress markers were also reduced in the Semax arm. The authors attributed these effects to a combination of antioxidant action and neurotrophin induction based on parallel animal data from their group. Limitations of this study include the relatively small sample size, the use of Russian-specific neurological rating instruments not uniformly validated against international scales (such as the NIHSS), and the absence of blinding in the primary administration (open-label design). These limitations prevent strong causal inference but the directional findings are consistent across multiple independent groups.

What this study tells researchers is that acute intranasal Semax at the doses used (reported as several hundred micrograms per administration in the nasal solution, equivalent to approximately 0.6-1.2 mcg/kg in these patients) appears to produce measurable neurological outcomes in a clinical population. The open-label design limits the signal but the size of the reported effect makes a pure placebo explanation less parsimonious. A properly powered, double-blind RCT has not been published in indexed literature as of May 2026.

Study 2: BDNF and TrkB mRNA Upregulation (Dolotov et al.)

Dolotov and colleagues published a detailed mechanistic rodent study examining the effect of single intranasal Semax doses on BDNF and TrkB receptor mRNA in rat frontal cortex and hippocampus. ^[7] Wistar rats received intranasal Semax at doses of 25 mcg/kg or 50 mcg/kg, with sacrifice and brain tissue collection at 1, 3, and 6 hours post-administration. mRNA quantification was performed by RT-PCR, with results normalized to beta-actin housekeeping gene expression.

BDNF mRNA in frontal cortex increased approximately 1.6-fold at the 25 mcg/kg dose and approximately 2.1-fold at the 50 mcg/kg dose at 1 hour, with levels returning toward baseline by 6 hours. TrkB mRNA showed a parallel increase of approximately 1.4-fold and 1.8-fold at the respective doses. The hippocampus showed smaller but directionally consistent changes. No changes were seen in the cerebellum, providing anatomical specificity to the result. The authors did not measure protein levels or downstream TrkB phosphorylation, and the study design does not allow determination of whether this mRNA increase translates into functionally relevant BDNF protein changes at synapses. Nonetheless, the study provides the strongest direct molecular evidence for the BDNF hypothesis and has been replicated by at least one independent group in rodents.

For researchers using Semax as a tool to study BDNF pathway dynamics, this dose-response data in rat frontal cortex is the most granular publicly available reference point.

Study 3: Cognitive and Attention Effects in Healthy Volunteers (Kost et al.)

Kost and colleagues investigated the cognitive effects of Semax in a randomized placebo-controlled design in healthy human volunteers. ^[11] The trial enrolled 18 healthy adults (age 22-35) and employed a crossover design where each subject received intranasal Semax and placebo in separate sessions separated by one week. Cognitive testing included a battery assessing selective attention, working memory, and processing speed, using computerized neuropsychological tests.

Semax administration was associated with significantly faster processing speed and improved accuracy on selective attention tasks relative to placebo, with effects peaking at approximately 1-2 hours post-administration and returning to baseline by 4 hours. Working memory tasks showed a non-significant trend toward improvement. The study is notable for being one of the few English-accessible controlled crossover trials in healthy subjects. Its primary limitations are the small sample size (n=18), the single-session design that precludes assessment of repeated dosing effects, and the absence of plasma or CSF pharmacokinetic sampling. The effect sizes for the attention measures were in the moderate range (Cohen's d approximately 0.5-0.7), which is promising but requires replication in larger cohorts.

For researchers modeling short-term nootropic interventions in animal analogs, this study provides a temporal profile (peak at 1-2 hours, washout by 4 hours) that can inform experimental design.

Study 4: Neuroprotection in Cerebral Ischemia Rodent Model (Grivennikov et al.)

Grivennikov and colleagues conducted a series of rodent experiments examining Semax's effects in models of transient focal cerebral ischemia (middle cerebral artery occlusion, MCAO). ^[9] In the primary experiment, Wistar rats underwent 60-minute MCAO with reperfusion. Animals were treated with intranasal Semax (50 mcg/kg) administered at 30 minutes post-reperfusion and again at 24 and 48 hours. Brain infarct volume was measured at 72 hours by TTC staining of coronal sections; neurological deficits were scored using a standardized rodent scale.

The Semax-treated animals showed a statistically significant reduction in infarct volume of approximately 35% compared with vehicle-treated controls. Neurological deficit scores were also significantly improved at 72 hours. Tissue analysis revealed reduced MDA levels and reduced IL-1beta immunostaining in the peri-infarct zone of Semax-treated animals. The authors proposed that reduced lipid peroxidation and inflammatory cytokine signaling in the ischemic penumbra contributed to infarct volume reduction. A notable limitation is that the treatment was initiated 30 minutes post-reperfusion, which is a relatively early and clinically achievable window; whether the same protection holds for longer delays to treatment was not systematically examined in this report.

This study is important for researchers using focal ischemia models because it provides specific coordinates within the experimental design (50 mcg/kg, intranasal, first dose at 30 min post-reperfusion) that demonstrated efficacy in this model system.

Study 5: Semax in Optic Nerve Disease (Kalinina et al.)

An unexpected application of Semax emerged from a clinical series by Kalinina and colleagues examining its use as an adjunct in patients with primary open-angle glaucoma and optic neuropathy. ^[12] In a 30-patient open study, subjects received intranasal Semax over 10 days as an adjunct to standard glaucoma therapy. Visual field parameters and pattern electroretinogram (pERG) amplitudes were measured before and after the course. The Semax group showed improvements in pERG amplitude and some visual field indices that were not observed in a matched historical control group receiving standard therapy alone.

This application is mechanistically coherent given Semax's proposed BDNF-upregulating effects, since BDNF is a well-characterized survival factor for retinal ganglion cells, the cell population lost in glaucoma. The study is limited by its open design, historical control comparison (rather than concurrent randomized controls), and small sample. It does, however, open a research avenue for investigators interested in Semax as a tool for studying BDNF-dependent retinal ganglion cell survival in rodent glaucoma models, where better-controlled animal studies could be designed.

Study 6: Gene Expression Profiling After Semax Administration

Malkova and colleagues used microarray gene expression analysis to characterize the transcriptional response in rat frontal cortex following acute Semax administration. ^[13] The study identified upregulation of multiple genes in the BDNF signaling cascade, including Arc (activity-regulated cytoskeleton-associated protein), Egr1 (early growth response protein 1), and several immediate-early genes associated with synaptic plasticity. Downregulated gene sets included several pro-apoptotic genes and transcripts associated with neuroinflammation. The study provided the broadest transcriptional picture of Semax's molecular effects available in indexed literature and is consistent with the mechanistic hypotheses discussed above, but the profiling approach generates hypotheses rather than confirming specific causal pathways.

Pharmacokinetics

Semax's pharmacokinetic profile is less well characterized than most approved pharmaceuticals, particularly in humans. The available data is primarily from rodent studies, with limited single-timepoint human data from early clinical development reports.

The dominant route of administration in published research is intranasal, both because Semax was developed as a nasal solution and because intranasal delivery bypasses first-pass metabolism and offers a credible CNS delivery pathway through olfactory epithelium. ^[3] Parenteral (subcutaneous or intraperitoneal) routes have been used in some rodent studies when controlled systemic dosing was needed for mechanistic experiments.

The short plasma half-life of 20-30 minutes by intranasal route and approximately 8-12 minutes by intravenous route in rodents reflects rapid proteolytic degradation by plasma and tissue peptidases. The Pro-Gly-Pro tail extends survival compared with the parent ACTH(4-7) tetrapeptide, but Semax is still a short linear peptide and subject to aminopeptidase and endopeptidase attack once in circulation. Degradation products are expected to be individual amino acids and dipeptides with no significant pharmacological activity at the concentrations produced, though the ACTH(4-7) fragment produced by cleavage of the Pro-Gly-Pro tail retains potential melanocortin activity in principle.

The practical implication for researchers is that experimental protocols requiring sustained receptor occupancy would need repeated dosing or continuous infusion, and that endpoint measurements should be timed carefully relative to the last dose. The 1-3 hour window for peak transcriptional effects on BDNF mRNA observed by Dolotov et al. is consistent with a compound that reaches its CNS target within 15-30 minutes and then is gradually cleared over the next 1-2 hours. ^[7]

Purity and Verification

What to Expect on a Certificate of Analysis

A legitimate research-grade Semax CoA should contain, at minimum, the following analytical results:

HPLC purity: The chromatogram should show a single dominant peak representing the target peptide, with an integrated purity of 98% or higher by UV absorbance at 214-220 nm (amide bond absorbance). The retention time should be consistent with the compound's expected hydrophobicity profile. Any peaks larger than 0.5% of the main peak should be identified where possible.

Mass spectrometry confirmation: Either electrospray ionization (ESI-MS) or matrix-assisted laser desorption/ionization (MALDI) data should show a monoisotopic or average mass consistent with the theoretical molecular weight of MEHFPGP (~813.9 Da). The ESI spectrum typically shows multiply charged ions; researchers should confirm the deconvoluted mass. A mass error of more than 0.5 Da from the theoretical value should trigger inquiry with the vendor.

Amino acid analysis or sequence confirmation: Higher-tier CoAs include amino acid composition analysis or even partial Edman degradation sequence data. These are not universal but are best practice for a research peptide where receptor pharmacology depends on exact sequence.

Residual solvents and counter-ion: The acetate content (or trifluoroacetate content) should be reported. TFA (trifluoroacetate) residues from HPLC purification have potential cytotoxic effects at elevated concentrations in cell-based assays; vendors should either use acetate exchange purification or quantify residual TFA to allow researchers to account for it.

Endotoxin testing: For any experiment involving cell culture or animal injection, bacterial endotoxin (LAL test) data on the batch is important. Lipopolysaccharide contamination is a common confound in peptide research, particularly in studies examining inflammatory markers.

Independent Verification Approach

Researchers who want to independently verify Semax purity before use can submit a sample to a third-party analytical laboratory offering peptide characterization services. Services such as those offered through university chemistry department analytical cores or commercial contract laboratories can provide HPLC-MS confirmation for a modest fee. The process involves dissolving a small aliquot (typically 0.1-0.5 mg) in aqueous buffer and submitting for reverse-phase HPLC with inline mass detection.

For labs with in-house HPLC capability, a simple single-run reverse-phase separation on a C18 column with a water/acetonitrile gradient and UV detection at 214 nm provides a rapid purity check. Comparing the measured retention time against a reference standard (available through Sigma-Aldrich or Bachem for some ACTH fragments) gives additional confidence. See our guide to reading and interpreting supplier CoAs for a step-by-step workflow.

Apollo Peptide Sciences publishes batch-specific CoA data linked from individual product pages, which this site independently verified for the current batch. Researchers are advised to request the CoA for the specific batch number included with their order and not accept a generic documentation placeholder.

Dosage and Reconstitution

Literature-Reported Research Doses

Published animal studies have used a fairly consistent dose range for intranasal administration in rodents. The most commonly reported doses in rat studies fall between 25 mcg/kg and 250 mcg/kg per administration, with 50 mcg/kg being the most frequently used dose in neurotrophin and neuroprotection models. ^[7][9] The Russian clinical literature reports intranasal human doses in the range of 200-2400 mcg per administration (as a nasal solution containing 0.1% Semax, with 2-3 drops per nostril delivering approximately 50-100 mcg per drop), but these figures come from studies conducted under conditions and regulatory oversight not applicable to independent research outside those settings. ^[10]

For subcutaneous administration in rodent studies, doses of 50-100 mcg/kg have been used when investigators needed to control for consistent systemic exposure. Intraperitoneal administration has also been used at similar doses in mechanistic studies. The route of administration significantly affects both the dose required and the pharmacokinetic profile, with intranasal delivery achieving CNS concentrations at lower systemic doses due to direct olfactory nerve transport.

Reconstitution Calculations: Worked Examples

Example 1: 10 mg vial, target concentration 1 mg/mL

Adding 10.0 mL of bacteriostatic water to a 10 mg lyophilized vial yields a 1 mg/mL (1000 mcg/mL) solution. At this concentration, 50 mcg/kg for a 250 g rat requires 0.05 mcg/g x 0.25 g/mcg (per gram body weight) = 12.5 mcg total = 0.0125 mL (12.5 microliters). This volume is practical for intranasal delivery using a micropipette and soft catheter or for subcutaneous injection.

Example 2: 10 mg vial, target concentration 0.5 mg/mL for higher-volume intranasal delivery

Adding 20.0 mL bacteriostatic water yields 0.5 mg/mL. For a 300 g rat at 50 mcg/kg, total dose = 15 mcg, volume = 0.030 mL (30 microliters). Thirty microliters is at the upper practical limit for rodent intranasal delivery without risk of laryngeal aspiration; the standard guidance is to keep intranasal volume in rats to 10-20 microliters per nare. Researchers using higher volumes should consider divided administration across both nares.

Example 3: Calculating doses for a mouse study at 100 mcg/kg

A 25 g mouse at 100 mcg/kg requires 2.5 mcg total. Using a 1 mg/mL stock, this requires 2.5 microliters. This volume is extremely small and practically challenging for intranasal delivery; subcutaneous administration in a slightly larger volume of the same stock is often preferred in mouse studies. A dilution to 0.1 mg/mL (100 mcg/mL) allows delivery of 25 microliters, which is more workable for SC injection with a 28-30 gauge insulin syringe.

For comprehensive guidance on dilution calculations, volume planning, and syringe selection for research peptide reconstitution, see our full protocol at /guides/how-to-reconstitute-peptides and /guides/how-to-calculate-dosage.

Storage After Reconstitution

Reconstituted Semax solution should be stored at 2-8°C and used within 28 days. Bacteriostatic water (containing 0.9% benzyl alcohol as preservative) extends in-solution stability compared with non-preserved sterile water. Researchers should avoid repeated freeze-thaw cycling of the reconstituted solution, as mechanical ice crystal formation during freezing can disrupt peptide structure. Aliquoting the reconstituted stock into single-use volumes before storage is the recommended approach for longer studies.

Side Effects and Safety

Preclinical Safety Data

Acute toxicity studies in rodents have reported a favorable preclinical safety profile for Semax. LD50 values in mice and rats administered intranasal or intraperitoneal Semax have been reported to be orders of magnitude above the effective research doses, with no acute mortality observed at doses substantially exceeding the pharmacologically active range. ^[14] The absence of significant adrenal stimulation at research doses distinguishes Semax from full ACTH and reduces the risk of corticosteroid-related adverse effects that would complicate interpretation of research data.

In subchronic rodent studies, repeated intranasal dosing over 10-30 days did not produce histopathological changes in brain, liver, kidney, or nasal mucosa in the studies reviewed. Body weight, food intake, and standard clinical chemistry parameters were not significantly altered. ^[14] Behavioral toxicity assessments, including forced swim test and rotarod performance, did not show impairment, which is relevant because some CNS-active compounds produce sedation or motor impairment that confounds cognitive testing.

Observations from Russian Clinical Literature

The registered clinical experience with Semax in Russia, primarily in stroke and optic neuropathy patients, has generally reported nasal mucosa irritation and transient nasal congestion as the most common adverse events, consistent with intranasal peptide administration rather than specific Semax toxicity. ^[10][12] No serious adverse events specifically attributable to Semax were reported in the trials reviewed, though the small sample sizes and open-label designs of most studies limit the ability to detect rare adverse events.

The absence of glucocorticoid axis stimulation (confirmed by cortisol and ACTH assays in clinical studies) is a notable safety feature that reduces the primary concern associated with ACTH-related peptides. ^[2] No effects on cardiovascular parameters, hepatic enzymes, or renal function were reported in the human studies, though systematic monitoring was not always rigorous.

Research Animal Welfare Considerations

For researchers planning animal studies with Semax, the favorable preclinical toxicity profile supports the use of standard monitoring protocols. Animals should be weighed twice weekly, and behavioral baselines should be established before any compound administration. Intranasal delivery in rodents carries the procedural risk of aspiration if volumes are excessive or delivery is too rapid; researchers should consult institutional animal care committee guidelines for intranasal peptide administration volumes.

Potential Interaction Concerns

Because Semax has monoaminergic effects (altered dopamine and serotonin metabolism reported in rodent studies), researchers using Semax in combination with compounds acting on these systems should design control experiments to separate the individual contributions. Studies combining Semax with dopaminergic drugs, selective serotonin reuptake inhibitors, or monoamine oxidase inhibitors in animal models would need careful pharmacological controls. ^[8]

How It Compares

Semax vs. Selank

Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro, TP-7) is the closest comparator in the Russian synthetic neuropeptide program. It is a heptapeptide derived from the immunomodulatory tetrapeptide tuftsin, also extended with Pro-Gly-Pro. ^[15] Both Semax and Selank were developed at the same institution, share the Pro-Gly-Pro stability motif, and have been studied in overlapping indications. The primary distinction is mechanistic: Selank is primarily characterized as an anxiolytic and immunomodulatory agent with effects on GABAergic neurotransmission and cytokine balance, while Semax is primarily nootropic and neuroprotective with stronger evidence for BDNF induction and melanocortin pathway engagement.

Researchers choosing between the two for a cognitive study model should note that Selank has a somewhat cleaner anxiolytic profile and may be preferred for anxiety-cognition interaction studies, while Semax's stronger BDNF induction data makes it more appropriate for neuroplasticity and neuroprotection paradigms. Both are available at similar price points and share the same intranasal research route. See our comparison guide at /best-for/nootropic-peptides for a detailed head-to-head.

Semax vs. Dihexa

Dihexa is a small molecule angiotensin IV analog designed by Harding and colleagues to engage the hepatocyte growth factor (HGF) / MET receptor system and produce synaptogenic effects. ^[16] Its preclinical evidence in rodent cognition models is notable, with some studies reporting effects at extraordinarily low doses (nanomolar range in CNS exposure). However, Dihexa has no published human clinical data and a substantially less mature safety profile than Semax. For researchers specifically interested in the BDNF pathway rather than the HGF/MET axis, Semax is the more appropriate tool. The two compounds work through non-overlapping mechanisms and could in principle be used in combination studies to probe pathway interactions, though no published literature on this combination exists.

Semax vs. N-Acetyl Semax

N-Acetyl Semax (sometimes listed separately by vendors) adds an N-terminal acetyl group to Semax. The claimed rationale is enhanced metabolic stability through protection of the free N-terminus from aminopeptidase attack. There is limited published evidence specifically comparing N-Acetyl Semax and Semax in controlled experiments, and most mechanistic claims for the acetylated form are extrapolated from the Semax literature. Researchers should treat N-Acetyl Semax as a distinct chemical entity with an unconfirmed advantage over the parent compound until controlled comparative data is published.

Where to Buy

Apollo Peptide Sciences is the vendor for this listing and offers Semax 10mg at $60.00 with batch-specific CoA data available on request. The CoA includes HPLC purity (reported as 98%+), ESI-MS confirmation of molecular weight, and batch number traceability. See the full Apollo Peptide Sciences vendor review for independent third-party test results from this site's quality verification program.

For the product page wrapping the affiliate link for this specific Semax 10mg listing, see /product/semax-2. The product page includes the most current pricing, batch documentation, and shipping information. We do not link directly to affiliate URLs in editorial content; the product page template handles outbound routing.

Researchers should also review our supplier selection guide before purchasing any research peptide, which covers CoA reading, red-flag indicators, and how to request third-party testing confirmation from vendors.

Open Research Questions

The Semax evidence base, while relatively substantial for a research peptide, contains several important unresolved areas that researchers should be aware of when designing studies.

Definitive receptor pharmacology: No peer-reviewed study in indexed literature has published a formal radioligand binding assay determining Semax's Ki at MC3R or MC4R, or demonstrated that MC4R knockout eliminates Semax's cognitive or BDNF-inducing effects in vivo. The melanocortin hypothesis is mechanistically coherent and supported by indirect data, but formal receptor deorphanization experiments using modern GPCR pharmacology tools have not been published for Semax specifically. ^[5]

Human pharmacokinetics: There is no published formal pharmacokinetic study in humans characterizing Cmax, Tmax, AUC, volume of distribution, or clearance for intranasally administered Semax. Dose-response relationships in humans cannot be reliably established without this data.

Long-term repeated dosing effects: Most published animal studies involve acute or short-course (7-14 day) administration. Whether repeated Semax administration produces receptor desensitization, tolerance to the BDNF-inducing effect, or other adaptive changes with longer exposure has not been examined in published indexed literature.

Protein vs. mRNA: The BDNF mRNA induction data is relatively robust, but studies measuring BDNF protein, synaptic BDNF release, and downstream TrkB phosphorylation in vivo are sparse. mRNA levels do not reliably predict functional protein changes, and the translational step is where many proposed neurotrophic effects of research compounds fail to materialize.

Pro-Gly-Pro biological contribution: Whether the C-terminal Pro-Gly-Pro contributes independent biological activity (as it does in some extracellular matrix signaling contexts) or simply serves as a stability scaffold has not been rigorously tested for Semax by comparing it directly with ACTH(4-7) and with an inert-tail Semax analog in the same experimental system.

International clinical validation: All controlled clinical data originates from studies conducted in Russia, with methodological standards and reporting conventions that differ from ICH-GCP guidelines. An independent replication of the stroke trial findings in a properly blinded, NIHSS-primary-endpoint, IRB-registered RCT would substantially strengthen or challenge the clinical evidence base.

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