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Semax side effects: what is reported and what is unknown

Human studies, animal studies, and the gaps between them.

Russian human studies of intranasal Semax report few or no adverse effects, but most abstracts do not describe how side effects were collected, and no independent safety trial exists. Nasal irritation is possible with any nasal product, and long-term effects are unknown. Semax is not FDA-approved, and REMEVi does not currently offer it.

Semax is not FDA-approved. Since HHS’s October 2026 interim policy, a state-licensed 503A pharmacy may compound it on a patient-specific prescription under listed conditions.

REMEVi does not currently offer Semax.

Reported in human studies

  • A 1997 review by the developers reported no negative side effects or complications in the patients treated, as stated by the authors.
  • The 2018 stroke study and the 2007 motor neuron disease study abstracts do not report adverse effects either way.

Reports from the developing group, without a stated method for collecting side effects, are not evidence that there are none. We found no independent safety trial of Semax outside Russia.

Reported in animal studies

The animal studies we could open measured brain chemistry, such as BDNF and other nerve growth factor genes in rats, rather than harms. They do not tell you which side effects people may have.

What is unknown

  • Long-term effects of repeated courses.
  • Effects at different solution strengths and amounts; no dose-comparison trial exists.
  • Interactions with other medicines.
  • Effects in pregnancy, breastfeeding, children and teens.
  • Whether the results of small Russian studies hold up in independent trials.

Intranasal effects

Any nasal spray or drop can cause stinging, a runny or dry nose, sneezing or a nosebleed. These are general effects of the nasal route, not findings from Semax studies. A product that is not prepared to pharmacy standards adds the risk of contamination, which is one reason the policy requires a licensed 503A pharmacy and a documented bulk source.

Call 911 for signs of a severe allergic reaction, such as trouble breathing, swelling of the face or throat, or hives over the body.

Who should not use Semax without a provider’s review

  • Anyone pregnant, trying to become pregnant or breastfeeding: no data exist.
  • Anyone under 18.
  • Anyone with active cancer or a history of cancer: tell your provider.
  • Anyone with a known allergy to Semax or to any ingredient in the product.
  • Anyone taking other medicines or supplements: tell your provider about all of them.

Is Semax safe?

There is not enough independent evidence to answer that. Semax is not FDA-approved, the human studies are small and mostly from the group that developed it, and most abstracts do not describe how side effects were tracked. A licensed provider can weigh what is known against your own health history before any decision is made.

Report a side effect

You or your provider can report a side effect to FDA MedWatch. Under the HHS policy, serious adverse events from a covered compounded product must be reported to MedWatch.

FDA MedWatch: report a problem

Sources

  1. Ashmarin et al., Zh Vyssh Nerv Deiat Im I P Pavlova 1997 — A nootropic adrenocorticotropin analog 4-10, Semax (15 years of experience in its design and study) (read November 2, 2026)
  2. Gusev et al., Zh Nevrol Psikhiatr Im S S Korsakova 2018 — The efficacy of semax in the treatment of patients at different stages of ischemic stroke (read November 2, 2026)
  3. Serdiuk et al., Zh Nevrol Psikhiatr Im S S Korsakova 2007 — Chronic partial denervation and quality of life in patients with motor neuron disease treated with semax (read November 2, 2026)
  4. Dolotov et al., Brain Res 2006 — Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus (read November 2, 2026)
  5. Agapova et al., Neurosci Lett 2007 — Neurotrophin gene expression in rat brain under the action of Semax, an analogue of ACTH 4-10 (read November 2, 2026)
  6. FDA — MedWatch: The FDA Safety Information and Adverse Event Reporting Program (read November 2, 2026)
  7. HHS — Enforcement Discretion Policy Regarding 503A Compounding Using Certain Peptide Bulk Drug Substances, 91 FR 68526 (Federal Register, October 30, 2026) (read November 2, 2026)
  8. Foley & Lardner, National Law Review 2026 — Peptides: HHS announces limited enforcement discretion for compounding six peptides (read November 2, 2026)

Medically reviewed by Linda West-Conforti, RN · CA RN #389453 ·