Semax vs Adamax, N-acetyl Semax amidate and Dihexa: what is the difference?

Evidence limits

What can this comparison not tell you?

A 2014 paper on how Dihexa works (Benoist et al., Journal of Pharmacology and Experimental Therapeutics, 2014) is marked as a retracted publication in PubMed, with a retraction notice published in 2025, so this page does not use it. The 2013 paper that describes Dihexa (McCoy et al., Journal of Pharmacology and Experimental Therapeutics, 2013) carries an expression of concern dated 22 September 2021 in its Crossref record, read on 14 October 2026, so this page reports no result from it. The table at the end of this page lists each name with its dated records. Online forum threads, which many searches for these names return, were not used: they are personal reports and not published studies.

What is the difference between Semax and Adamax?

Semax is a defined seven-amino-acid peptide with a published record, and the sources searched on 14 October 2026 held no peptide record under the name Adamax. Semax has the sequence Met-Glu-His-Phe-Pro-Gly-Pro, the formula C37H51N9O10S, 232 PubMed records and a registration as a drug in Russia (FDA briefing document, July 2026). A PubMed search for 'adamax AND semax' returned 0 records on 14 October 2026, and 'adamax' alone returned 39 records whose titles concern a machine-learning optimiser and not a peptide.

A ClinicalTrials.gov search for Adamax returned no record, and a text search on 14 October 2026 found it in none of the Poisons Standard, the FDA's July 2026 briefing document or the WADA 2026 Prohibited List, a name search only and not a ruling on any substance. No chemical record read for this page states a structure for it.

Because no paper, trial record or regulator document read for this page defines a peptide called Adamax, any statement about its structure, stability or effects comes from outside the records read, and this page does not repeat such statements. The FDA warns that derivatives sold under one common name can be different substances with different safety profiles (FDA briefing document, July 2026), so a shared stem in a name proves nothing about a shared record.

What is the difference between Semax and N-acetyl Semax amidate?

N-acetyl Semax amidate is a name for Semax with two edits: an acetyl group on the amino end of the chain and an amide on the carboxyl end. Semax itself has neither edit (FDA briefing document, July 2026). A PubMed search for 'N-acetyl semax', 'N-acetyl-semax' or 'Na-Semax' returned no record on 14 October 2026. In test-tube and cell experiments, acetylating the amino end of Semax changed how it binds copper ions, left the strength of zinc binding comparable and did not protect human neuroblastoma cells from copper toxicity, a test-tube and human neuroblastoma-cell result with no replicate count in the abstract that does not establish a human result (Magrì et al., Journal of Inorganic Biochemistry, 2016).

The amino end matters because enzymes called aminopeptidases clip Semax from that end. In test tubes with an aminopeptidase preparation, swapping the first amino acid changed how fast Semax was broken down, an enzyme-assay result from an abstract with no replicate count that does not establish a human result (Shevchenko et al., Russian Journal of Bioorganic Chemistry, 2011). A 2013 paper on the stability of 'Semax acetyl' exists, but the title does not show whether it means the acetate salt or an acetylated amino end, and its abstract was not available (Shevchenko et al., Doklady Biological Sciences, 2013). The Semax half-life page sets out what is known about breakdown.

What is the difference between Dihexa and Semax?

Dihexa and Semax are different molecules with different origins. Semax is a seven-amino-acid analogue of an ACTH fragment, studied in Russia in people and animals (FDA briefing document, July 2026). Dihexa, also coded PNB-0408, is N-hexanoic-Tyr-Ile-(6)-amino hexanoic amide, an analogue of angiotensin IV, and the studies read for this page were in rodents (Wells et al., Journal of Huntington's Disease, 2024). In rat hippocampus, Semax produced a maximal 1.4-fold increase in the brain protein BDNF, an animal result from an abstract that gives no number of rats and does not establish a human result (Dolotov et al., Brain Research, 2006). The two sit in different families: one traces to a pituitary hormone, the other to a blood-pressure peptide.

A PubMed search for 'dihexa' returned 19 records on 14 October 2026, none tagged as a clinical trial or randomised controlled trial, and a ClinicalTrials.gov search found no record for Dihexa or its code PNB-0408. Its animal studies are mixed. In APP/PS1 mice, a mouse model of Alzheimer's disease, Dihexa restored water-maze performance, a mouse result from an abstract that gives no group sizes and does not establish a human result (Sun et al., Brain Sciences, 2021). In 40 male rats randomised to three groups in a model of Huntington's disease, Dihexa did not protect the animals from the induced deficits, a rat result that does not establish a human result (Wells et al., Journal of Huntington's Disease, 2024).

No record read for this page lists either molecule as an approved medicine in Australia or the United States. The Semax legal status page gives the dated records for Semax, and the same text search of the Poisons Standard found no entry naming Dihexa (read 14 October 2026).

Is Semax or Dihexa better?

The sources searched on 14 October 2026 did not find a study that compares the two, so this page cannot rank them. 'Better' needs a stated outcome, a model and a comparison in the same experiment, and none of the published Semax or Dihexa papers read for this page compares the two. Semax has small human studies in stroke, optic nerve disease, motor neuron disease and other conditions, with limits described on the Semax study findings page. No human study of Dihexa was found in the sources searched.

A common mistake is to treat the amount of published work as a measure of merit. A compound with more papers has been studied more, and that says nothing about whether the studies were good or the results favourable.

Has any study compared Semax with other peptides?

The sources searched on 14 October 2026 did not find a study that ranks Semax against other peptides overall. Researchers have compared Semax with other compounds on narrow questions. In rodent pain tests, Semax decreased pain sensitivity in all the models used, while lower amounts of the ACTH(4-10) fragment it is built from produced no analgesic effect, a rodent result from an abstract that gives no group sizes and does not establish a human result (Ivanova et al., Bulletin of Experimental Biology and Medicine, 2007).

In cultured rat PC12 cells, another peptide preparation improved survival and differentiation while Semax produced no trophic effect, a cell-culture result from an abstract with no replicate count that does not establish a human result (Safarova et al., Bulletin of Experimental Biology and Medicine, 2002). In rats with 6-OHDA-induced parkinsonism-like damage, neither Semax nor Selank affected motor activity, and Selank decreased anxiety level, a rat result from an abstract that gives no group sizes and does not establish a human result (Slominsky et al., Doklady Biological Sciences, 2017). Each result applies to its own test.

In male rats in a chronic unpredictable stress model, Semax and a second ACTH(4-10) analogue each reversed or substantially attenuated stress-induced loss of sucrose preference and a fall in hippocampal BDNF, while the forced swim test showed no effect of the stress or the peptides, a rat result from an abstract with no group sizes that does not establish a human result (Inozemtseva et al., European Journal of Pharmacology, 2024). In 52 healthy participants, scans taken before and 5 and 20 minutes after Semax, Selank or placebo showed between-group differences in connectivity between the right amygdala and right temporal regions, in a small study that measured connectivity and not health outcomes (Panikratova et al., Doklady Biological Sciences, 2020). Selank and Semax are different peptides.

What have studies found about Semax, focus, anxiety and brain fog?

A PubMed search on 14 October 2026 for Semax together with 'brain fog' returned no record. A 1997 review by Semax's developers is the only source read that discusses memory and attention in healthy men under extreme conditions, and its abstract gives no individual measurements and no participant numbers, so this page reports no result from it (Asmarin et al., 1997). For anxiety, rats given Semax as pups showed a decreased anxiety level in tests at four to eight weeks of age, a rat result from an abstract that gives no group sizes and does not establish a human result (Sebentsova et al., Zhurnal Vysshei Nervnoi Deiatelnosti, 2005).

A PubMed search for Semax with anxiety or anxiolytic returned 18 records on 14 October 2026, and judging by their titles, 17 are animal or laboratory studies and one is a healthy-adult brain-scan study (Panikratova et al., 2020).

The FDA describes antidepressant- and anxiolytic-like findings in rodents, which do not establish effects in people (FDA briefing document, July 2026). The FDA did not evaluate ADHD because it did not find supporting literature (FDA briefing document, July 2026). A 2007 paper proposed Semax as a candidate for ADHD, as a hypothesis and not a result (Tsai, Medical Hypotheses, 2007).