Nootropic

Semax Peptide

Reviewed 22 October 2026 · How we research

Also known as: ACTH(4-10) analogue, N-Acetyl Semax

What is Semax?

Semax is a seven-amino-acid peptide based on a fragment of adrenocorticotropic hormone (ACTH 4–7) with a Pro-Gly-Pro tail added to protect it from breakdown. It has no hormonal (steroid-releasing) activity but keeps ACTH fragments' effects on the brain.

It was developed in the Soviet Union and is registered in Russia as a nasal drop for stroke recovery, cognitive disorders and optic-nerve disease. Elsewhere it is known mainly as a research nootropic.

How Semax works

Rat studies show Semax rapidly increases brain-derived neurotrophic factor (BDNF) and its receptor TrkB in the hippocampus — signals involved in learning, memory and neuronal survival. It also modulates dopamine and serotonin systems and affects expression of genes related to inflammation and blood vessels after experimental stroke.

What the research shows

A single intranasal dose increased BDNF and TrkB expression in rat hippocampus (Dolotov et al., 2006).
Russian clinical studies report improved recovery after ischaemic stroke; these are mostly small and not widely replicated outside Russia.
Animal studies show improved learning and attention tasks.

Compare: Semax vs Selank

Semax side effects

Russian clinical use reports good tolerability. Reported effects include nasal irritation, headache and, rarely, anxiety or irritability. There are no large Western safety trials.

UK legal status

Semax is not licensed in the UK. It is not a controlled drug, so possession is not an offence, but it cannot be sold for human use. “Semax nasal spray UK” products are research chemicals.

More detail, including current UK research-vial prices: Semax UK guide. For the doses used in published studies and the reconstitution maths: Semax dosing in the literature.

Semax: frequently asked questions

What does Semax do?

In rats it rapidly raises BDNF in the hippocampus. In Russia it is used as a nasal drop for stroke recovery and cognitive disorders.

Is Semax legal in the UK?

It is not a controlled substance, but it is unlicensed and cannot be sold for human consumption.

Semax vs Selank?

Semax is studied mainly for cognition and stroke; Selank mainly for anxiety. See Semax vs Selank.

What is N-Acetyl Semax?

A modified version with an acetyl group intended to increase stability. It has far less published research than standard Semax.

References

Dolotov OV, et al. Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Res. 2006;1117:54–60.
Medvedeva EV, et al. The peptide Semax affects the expression of genes related to the immune and vascular systems in rat brain focal ischemia. BMC Genomics. 2014;15:228.

Related compounds