Semax and Selank: what is the difference for focus and stress?

Why are they compared?

Someone looking for help concentrating might encounter Semax; someone looking into stress may encounter Selank. Both are discussed as peptides affecting brain-related processes, but “focus” can mean attention, memory, fatigue or difficulties caused by poor sleep or stress. “Stress” can mean a temporary response or symptoms that deserve professional assessment. An ingredient name alone does not identify the underlying question.12

What did the Semax study measure?

A 2018 experiment compared intranasal Semax with placebo in 24 healthy volunteers and measured brain activity patterns using functional MRI before and shortly after administration. The authors reported a difference in a brain-network measure. A scan pattern is not a direct measure of better concentration, memory or daily functioning, and this small short study cannot establish long-term safety. Read the Semax profile, including the separate stroke research and its limitations. A later scan study included both names in separate groups: compare the two imaging reports. Stroke research is a separate clinical question: see the Semax recovery reports.1

What did the Selank studies measure?

A 2014 report compared Selank with an anxiety medicine in 60 people with anxiety-related and somatoform disorders. Its English abstract reports an anxiety-reducing effect. It does not give enough detail about allocation, blinding, placebo or numerical differences to establish equivalence or how much effect was caused by Selank. The full Russian-language paper was not reviewed here. See the Selank profile for this report and another small comparison. For the other comparisons, including the add-on study, see what the Selank anxiety reports actually say.2

Are products with the same name interchangeable?

No. A study may concern a specific intranasal product, population and outcome; an online vial or a product used by a different route is a separate question. An ingredient certificate can help identify what was tested, but does not establish that the finished product works or is suitable for use. Learn what a certificate of analysis can and cannot show.

The US FDA identifies potential immune-reaction risks from aggregation and peptide impurities in compounded Semax and Selank acetate for certain routes, and says safety information is limited or missing. This is an assessment of nominated compounding substances, not proof that every product causes harm.34

What is a useful next step?

For an ongoing difficulty with memory, concentration, sleep or anxiety, consider the particular symptoms and their impact rather than assuming a peptide addresses the cause. A qualified clinician can help assess causes and discuss options. Explore focus and memory or stress and mood for broader context.4