What Is Semax? Dosage, Half-Life & How to Track It

What Semax is and how it works

Semax is a synthetic heptapeptide built from a fragment of adrenocorticotropic hormone (ACTH) — specifically the ACTH(4–10) region, modified to strip out ACTH’s hormonal (cortisol-raising) activity while keeping its effect on the brain. It was developed in Russia in the 1980s and has been sold there for decades as a prescription nasal-drop nootropic.

The proposed mechanism runs largely through BDNF — Semax appears to increase expression of this neurotrophic factor, which supports neuron survival and the formation of new synaptic connections. It is also studied for its effect on dopamine and serotonin turnover, and has clinical history in Russia and Ukraine for ischemic stroke and cognitive recovery, alongside informal use as a focus aid.

Almost all of that clinical evidence is intranasal, using the original 0.1%/1% drop formulations; Semax is not FDA-approved for any use in the US, and rigorous Western trials are limited. Treat the mechanism as reasonably well characterized and the outcomes data as encouraging but thin outside Russia.

Typical dosing & reconstitution

For subcutaneous use, Semax is reconstituted with bacteriostatic water from a lyophilized vial and dosed 200–500 mcg once daily, typically titrated upward across several weeks. That is a different route from the clinical literature, which is almost entirely intranasal — drops delivering 400–900 mcg/day split into two or three applications; injecting it is a community adaptation for people using research-peptide vials rather than the pharmacy nasal spray.

Reconstitution options set your concentration and dose-per-unit:

At 1.67 mg/mL, a 300 mcg dose is 18 units on a U-100 insulin syringe. The reconstitution calculator handles the same math for any vial size and water amount, whichever route you use it by.

Half-life & what it means for frequency

Semax’s parent peptide is broken down quickly — its measured half-life in blood is short, on the order of minutes. Subcutaneous injection is reported to give more sustained systemic absorption than intranasal drops, part of the rationale some people give for switching routes, even though it departs from the studied protocol.

As with Selank, the short blood half-life doesn’t mean the cognitive effect vanishes just as fast — users commonly report a single dose’s focus effect lasting several hours, consistent with the idea that active breakdown fragments, not the intact parent peptide, carry some of the downstream effect. That is why once-daily dosing, not round-the-clock dosing, is the standard pattern.

What to track & common side effects

Semax is generally reported as well tolerated at studied doses. The most-cited side effects are mild — injection- or nasal-site irritation, occasional anxiety or jitteriness at higher doses, and trouble sleeping if dosed too late in the day.

What is worth tracking is subjective and easy to lose without a log: focus, mental energy, and mood on days you dose versus days you don’t, plus the dose and time of day — since a dose taken too late is a common, avoidable cause of sleep complaints.

Frequently asked questions