Semax-Amidate

Semax-Amidate, formally N-Acetyl Semax Amidate (Ac-Met-Glu-His-Phe-Pro-Gly-Pro-NH2, MW ~855 Da), is a dual-modified synthetic heptapeptide derived from Semax, which is itself an analogue of the adrenocorticotropic hormone (ACTH) fragment 4–10. The N-terminal methionine carries an acetyl group and the C-terminal proline is amidated. These additions block the two principal sites of enzymatic degradation: N-terminal acetylation resists leucine aminopeptidase cleavage, while C-terminal amidation resists carboxypeptidase attack. The result is a theoretically extended plasma and tissue half-life relative to the parent compound, whose unmodified intranasal half-life is on the order of minutes. No published pharmacokinetic study has confirmed the exact magnitude of this extension for the amidated form.

The ACTH(1–3) sequence responsible for adrenocortical activity is absent from the parent scaffold, so Semax and its variants are not expected to stimulate cortisol release.

The precise receptor target remains incompletely characterized. In vitro and animal evidence indicates that the ACTH(4–10) fragment and its analogues interact with melanocortin receptors MC4 and MC5, where the peptide appears to act as a partial agonist or competitive antagonist against alpha-MSH. The peptide also inhibits enkephalin-degrading enzymes (IC50 approximately 10 µM in the parent compound), potentially sustaining endogenous opioid tone.

The best-documented downstream effect is rapid upregulation of brain-derived neurotrophic factor (BDNF) and its high-affinity receptor TrkB in hippocampal tissue, alongside activation of serotonergic signaling (elevated striatal 5-HIAA) and potentiation of dopaminergic responses to stimulants. Cholinergic neuron survival is also reported to increase in primary basal-forebrain cell cultures at nanomolar concentrations.

No independent clinical trial has been conducted specifically on Semax-Amidate. All human evidence pertains to the parent compound, unmodified Semax; extrapolation to the amidate form is mechanistically plausible but unverified in human subjects.

For unmodified Semax, the following human studies exist. Kaplan et al. (1996, Neuroscience Research Communications 19:115–123) administered intranasal Semax at 16 µg/kg to healthy volunteers and reported significant improvements in attention and short-term memory, together with EEG changes characteristically associated with nootropic activity. Full methodological details—including blinding and exact sample size—are not available from secondary sources, limiting interpretation.

Lebedeva et al. (2018, PMID 30225715, n=24 healthy volunteers, 14 Semax / 10 placebo) used resting-state fMRI and found that a single intranasal dose of 1% Semax produced measurable expansion of the default mode network in the medial frontal cortex at 5 and 20 minutes post-dose relative to placebo.

Gusev, Martynov, and colleagues (published 2018, n=110 ischemic stroke patients, non-randomized) administered two 10-day intranasal Semax courses (6,000 µg/day) separated by a 20-day interval. Plasma BDNF levels rose in both early-rehabilitation (89 ± 9 days post-stroke) and late-rehabilitation (214 ± 22 days post-stroke) subgroups, with correlated improvements on the Barthel Index and MRC motor scale. The absence of randomization and blinding substantially limits causal inference.

In rodents, Dolotov et al. (2006, PMID 16996037) showed a single intranasal dose (50 µg/kg) produced a 1.4-fold rise in hippocampal BDNF protein, a 3-fold increase in BDNF mRNA, and improved conditioned avoidance performance. Dmitrieva et al. (2009, PMID 19633950) documented selective upregulation of BDNF, TrkC, TrkA, NGF, and NT-3 transcription in ischemic rat cortex after middle cerebral artery occlusion. Sciacca et al. (2022, PMID 35080861) reported that Semax binds Cu2+ ions with high affinity (cKd ~1.3×10−15 M), inhibiting copper-induced amyloid-beta aggregation and reducing Aβ1–42 cytotoxicity by up to 90% in neuronal cell cultures—an in vitro finding with speculative relevance to neurodegeneration.

Semax has been approved in Russia since 1994 for ischemic stroke, TIAs, and cognitive disorders; no Western regulatory body has approved any form of Semax or its amidate variant.

Typical dosage: 300-600 mcg (daily).

No regulatory dosing guidance exists for Semax-Amidate in any jurisdiction. The following reflects Russian clinical protocols for parent-compound Semax and extrapolated community research practice.

Approved Russian protocols for unmodified Semax (intranasal nasal spray) in ischemic stroke and rehabilitation: 1,200–12,000 µg per day divided across two daily sessions, for 5–14 day treatment courses. A 2018 stroke rehabilitation study used 6,000 µg/day in two 10-day courses separated by a 20-day washout.

For cognitive research use of the parent compound, studied doses in healthy volunteer settings have been lower—around 200–600 µg intranasally, in 2–3 daily applications over cycles of 10–14 days.

Community protocols for N-Acetyl Semax Amidate (anecdotal, not derived from clinical trials) most commonly report 100–300 µg per intranasal dose, one to two times daily. Because the dual terminal modification prolongs peptide exposure relative to unmodified Semax, many sources recommend beginning at the lower bound of this range (100 µg once daily) and assessing individual response before escalating. Reported cycle lengths range from 10 to 30 days, with rest periods of comparable length. These community-derived figures are not validated by pharmacokinetic studies.

This information is educational only and does not constitute medical advice. Semax-Amidate is not approved by the FDA, EMA, or comparable Western regulatory bodies, and appropriate dosing for any clinical context must be determined by a qualified healthcare professional.

No compound-specific stability data has been identified for this peptide. The general lyophilized-peptide handling framework applies — see Storage & handling for temperature, reconstitution diluent, and beyond-use dating principles.

All combination strategies for Semax-Amidate are anecdotal. No controlled study has examined co-administration with any other compound.

• Semax + Selank: The most frequently cited pairing in nootropic communities. Selank is an anxiolytic peptide derived from tuftsin; the claimed rationale is complementary activity—Semax for cognitive activation and BDNF upregulation, Selank for anxiety reduction. No pharmacokinetic or safety interaction data exist. Both compounds carry decades of Russian clinical use for their respective indications, but no comparative or combined-use trial has been published in peer-reviewed literature.

• Semax + BPC-157: Reported by some researchers combining neuroprotection goals with BPC-157's purported tissue-repair activity (documented in animal models only). No human data supports this combination.

• Semax + Cerebrolysin: Cited anecdotally for overlapping neurotrophic mechanisms. Cerebrolysin is a hydrolyzed porcine brain protein extract with limited clinical evidence in stroke and dementia; concurrent use with Semax has not been studied in any controlled setting.

The absence of interaction data means combining these agents multiplies pharmacological uncertainty. All combination claims should be treated as hypothesis-generating anecdote.

Semax-Amidate is not currently FDA-approved for any indication. Effective April 22, 2026, the FDA removed Semax-Amidate from Category 2 of its Section 503A bulk drug substances list after the original nominators withdrew their nominations. This removal lifts the prior “significant safety risk” designation but does not place Semax-Amidate on the 503A Bulks List. Compounding pharmacies may prepare it with a valid physician prescription and pharmaceutical-grade API from an FDA-registered manufacturer. The FDA’s Pharmacy Compounding Advisory Committee (PCAC) is scheduled to review this substance at its July 23–24, 2026 public meeting. Removed from FDA Category 2 effective April 22, 2026. Selected for PCAC review Day 2 — July 24, 2026. PCAC agenda: DSIP (Emideltide), Semax, Epitalon. NOT currently on 503A Bulks List — requires physician Rx. Source: FDA Advisory Committee Calendar / Lengea Law, May 2026.

PeptideSciences101 does not endorse vendors. For transparency metrics and third-party testing notes, see the vendor directory.

Reported side effects: Similar to Semax

Available safety data derives almost entirely from the parent compound, unmodified Semax, studied in Russian clinical settings. The amidate form has no independent safety record.

Adverse effects reported for Semax in Russian clinical datasets are predominantly mild and transient: nasal or nasopharyngeal irritation, occasional headache, and rare dysgeusia (metallic taste) occurring during or shortly after intranasal administration. Published trials of up to 30 days duration reported no clinically significant changes in vital signs, laboratory parameters, or ECG findings at therapeutic intranasal doses.

Because the ACTH(1–3) adrenocortical-stimulating sequence is absent from the scaffold, cortisol elevation is not expected; this has not been confirmed by rigorous human dose-escalation studies.

At higher doses or with late-day administration, stimulant-like effects have been reported anecdotally: heightened alertness, insomnia, anxiety, or agitation. The extended half-life conferred by dual terminal modification means that any adverse effect from Semax-Amidate—however mild—may persist longer per dose than with unmodified Semax.

No formal safety studies exist for Semax or Semax-Amidate in pregnancy, lactation, pediatric populations, or in patients with hepatic or renal impairment. No drug interaction studies have been published. Commercially sold research-grade Semax-Amidate products are subject to no pharmacovigilance monitoring, and purity standards vary by vendor. Acetylation and amidation are routine pharmaceutical chemistry techniques used in approved drugs, but this does not establish the safety of this specific compound in human use.