Semax

Semax is a synthetic chain of seven amino acids modeled on part of ACTH, the hormone the pituitary uses to signal the adrenal glands to make cortisol. That piece of ACTH keeps the hormone's effects on the brain without its hormonal ones, and a Pro-Gly-Pro ending is thought to slow its breakdown by enzymes [4]. Russian researchers developed it, and in Russia it is a registered drug in the form of 0.1% and 1% nasal drops [4]. American buyers find it online and at some wellness clinics, marketed as a nootropic for focus, memory and mood, as a nasal spray or an injection, sometimes mixed with its sibling peptide selank.

Unlike many peptides on these menus, semax has been given to people. The best-built human study scanned 52 healthy volunteers and found changes in how brain regions communicate, without testing whether anyone thought or remembered better [1]. FDA's 2026 review found too little evidence that it works for any condition it evaluated [4].

On October 28, 2026 an interim HHS policy let state-licensed pharmacies and physicians compound semax for nasal use, as the only active ingredient and under conditions, without expecting enforcement action [5]. Injections and semax-selank blends are not covered.

Most of what is known comes from rodents. A single dose raised levels of BDNF, a protein that supports nerve-cell growth and survival, in the rat hippocampus, and treated rats did better on a conditioned avoidance task [3]. In other rodent work it increased serotonin turnover in the striatum and, given before amphetamine, sharply boosted the dopamine release amphetamine caused [2].

FDA's reviewers read that same body of work as a set of loosely understood effects: nerve protection, blood thinning, pain relief and anxiety-like changes, all in animals [4]. The dopamine finding is one reason they raised abuse potential as an open question, since boosting dopamine in that part of the brain is something addictive drugs do.

The human imaging study is careful work. Participants received semax, selank or placebo and had resting-state fMRI before and after, with brain regions chosen in advance [1]. It found connectivity changes involving the right amygdala. It measured no memory, attention or task performance, and the volunteers had no deficit to correct.

FDA evaluated semax for cerebral ischemia, migraine and trigeminal neuralgia, the uses its nominators put forward, and found the evidence insufficient for all three [4]. Much of the clinical literature, including the stroke studies, is published in Russian, and FDA did not consider studies it could not read in a verified English translation. Effects of the kind sold in the US, sharper focus in healthy adults, have not been tested in a trial with a cognitive endpoint.

Grade C: a real human record of exposure and a plausible mechanism, with no outcome trial behind the use it is marketed for. Our evidence review covers the imaging study in more depth.

No dose has been validated for the uses semax is sold for. FDA found no study of how the human body absorbs or clears it by any route, and the human studies it reviewed used very different regimens, from a single nasal dose to drops three times a day for ten days [4]. Vendor protocols for daily nasal sprays or injections are not grounded in those studies.

The HHS policy covers intranasal semax free base only, compounded as a single ingredient from tested bulk peptide on a prescription for one patient [5]. The injections and semax-selank blends FDA found on sale fall outside it [4] [5].

FDA concluded there was not enough clinical information to describe semax's safety. Across the studies it reviewed, about 100 to 115 adults and 451 children had taken it intranasally, and most papers did not report on side effects. Its adverse-event database held one report through December 3, 2025: a consumer hospitalized with eye pain after using nasal drops bought online. FDA also flagged a possible blood-thinning effect, which could matter for people prone to bleeding or taking anticoagulants, and the untested abuse potential [4]. HHS, explaining its policy, judged those concerns theoretical, noting that the intranasal human record covers several hundred people without a reported adverse outcome [5].

Under the October 28, 2026 policy a covered pharmacy must buy semax from an FDA-registered facility with a certificate of analysis, label the product as compounded and not for resale, and pass serious harm or defects on to FDA through MedWatch [5]. The policy is interim, adds semax to no list, and can be revisited if a safety signal appears. A research-use-only nasal spray bought online has no prescriber, no tested source and no reporting behind it.