Semax monograph

Overview

Semax is a synthetic heptapeptide derived from the ACTH(4-7) fragment with a C-terminal Pro-Gly-Pro sequence added to improve stability. It is used in Russia and some nearby markets as a nootropic/neuroprotective medicine, but high-quality human data are limited and most mechanistic work is preclinical or from small human studies. For bodybuilding/performance use, the evidence is weak and the product is better thought of as experimental than as a proven performance aid. PubMed PMC[^1]

Pharmacokinetics & Mechanism

• Class: Synthetic ACTH(4-7) analog / neuropeptide / nootropic peptide
• Mechanism of action: Not well established in humans. Preclinical literature suggests Semax modulates neurotrophin signaling, stress-response pathways, and gene expression after ischemia; it has been reported to increase BDNF, NGF, TrkA/TrkB/TrkC-related transcription and to shift inflammatory vs neurotransmission-related expression patterns after cerebral ischemia. The peptide is also described as an ACTH(4-7) analog with no hormonal activity, so its effects are not via classic corticosteroid signaling. PubMed PMC PubMed
• Target(s): Best-supported targets are pathway-level rather than a single receptor: neurotrophin gene transcription (BDNF, NGF, NT-3 and their receptors TrkA/TrkB/TrkC), inflammatory signaling, neurotransmission-related genes, and broader brain-network effects on fMRI. A specific human receptor target is not established. Some reviews describe downstream interactions with dopaminergic and BDNF-related systems, but this remains inferential. PubMed PMC PubMed
• Route(s) of administration: Intranasal is the main clinical route in human reports and product use. Preclinical studies also use intraperitoneal or other laboratory routes, but those are not directly interchangeable with human use. PubMed PMC
• Onset: Intranasal CNS effects may begin within minutes; one human fMRI study detected changes at 5 and 20 minutes after a 1% intranasal dose. Clinical symptom onset for cognition/stroke-related outcomes is not well established. PubMed
• Half-life: Not well established in humans. Public peer-reviewed sources accessible here did not provide a validated human plasma half-life, and that is the right answer for a safety database. For extended/double-long variants sometimes marketed as Semax-D, robust human PK data are also not well established. PubMed PMC
• Metabolism / clearance: Likely rapid peptide degradation by peptidases, which is why the Pro-Gly-Pro tail was added to increase resistance to peptidases. Human clearance pathways and metabolites are not well established in authoritative sources available here. PMC