Semax
A stabilised fragment of ACTH with the hormonal activity removed, registered in Russia for stroke and cognitive indications. Evidence is almost entirely Russian.
Cognitive & Neuro
Cosyntropin
The first 24 amino acids of ACTH, used as the standard diagnostic test of adrenal function. Approved, well characterised, and used as a single dose.
Overview
ACTH is the pituitary hormone that tells the adrenal glands to make cortisol. Only the first 24 of its 39 amino acids are needed for that signal — the rest carry the species differences and much of the immune reactivity. Cosyntropin is that active portion. Give it, measure cortisol half an hour later, and you learn whether the adrenal glands can respond. If they cannot, adrenal insufficiency is confirmed.
A synthetic tetracosactide corresponding to ACTH(1-24), retaining full melanocortin-2 receptor agonist activity with substantially reduced immunogenicity relative to full-length ACTH. MC2R activation on adrenocortical cells raises cAMP, mobilising cholesterol via StAR and driving steroidogenesis. The short synacthen test measures serum cortisol at baseline and 30 and 60 minutes after a 250 mcg intravenous or intramuscular dose; a stimulated cortisol above the assay-specific threshold excludes primary adrenal insufficiency. A depot formulation is used therapeutically in some jurisdictions, notably for infantile spasms.
Research areas
Adrenal insufficiencyHPA axis testingCongenital adrenal hyperplasia
Dosing reported in the literature
Every protocol below is reproduced from a published study or approved labelling, with its source named. These are records of what was studied — not recommendations, and not a suggestion that any of them is appropriate for any person.
| Protocol as reported | Source |
|---|---|
| 250 mcg intravenously or intramuscularly with cortisol measured at 0, 30 and 60 minutes | Standard short synacthen test protocol |
| 1 mcg intravenously in the low-dose test, proposed as more sensitive for partial secondary adrenal insufficiency | Low-dose ACTH stimulation test literature |
Trial status
Long-established diagnostic standard with an extensive validation literature.
Reported safety signals
- Hypersensitivity reactions including anaphylaxis have been reported, more often in people with existing allergic disease.
- Recent glucocorticoid administration will confound the result.
- It is a diagnostic agent — it has no established role as a therapeutic outside the specific depot indications.
Common questions
Why is Semax related to cosyntropin?
Both derive from ACTH. Cosyntropin keeps the hormonally active 1-24 region and is used to stimulate cortisol. Semax is the 4-10 fragment, which lacks the region needed to trigger cortisol release and was developed for its behavioural effects instead.
Primary sources
Medical disclaimer
This page is for informational and research purposes only. Nothing here constitutes medical advice. The compounds discussed are research chemicals. Consult a qualified clinician before starting any protocol.
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