Corticotropin, also called adrenocorticotropic hormone or ACTH, is a peptide hormone normally released by the pituitary gland to stimulate the adrenal glands. A purified, long-acting formulation derived from it, sold as Acthar Gel (repository corticotropin injection), has been an FDA-approved prescription drug for decades — making it one of the oldest peptide drugs still in active use.
What It Is and How It Works
ACTH's natural job is to tell the adrenal cortex to produce cortisol and other corticosteroid hormones. Acthar Gel is a highly purified, porcine-derived formulation of ACTH suspended in a gel that slows its release after injection. Its primary documented mechanism is stimulating the body's own cortisol production, though some researchers have proposed that ACTH may also have direct anti-inflammatory or immune-modulating effects through a separate receptor pathway, independent of raising cortisol. That secondary mechanism is still debated in the research literature rather than settled.
What It's Approved For
Acthar Gel's FDA label covers a notably broad range of uses, including infantile spasms (West syndrome) in children under two, flares of multiple sclerosis, and adjunctive short-term therapy during flares of various rheumatic, collagen, dermatologic, allergic, ophthalmic, and respiratory conditions, among others. That breadth is itself part of the drug's story: the original version of this product was first approved before the modern framework requiring well-controlled clinical trials for every claimed use was put in place industry-wide in the early 1960s. Several of its currently labeled indications were established under older evidentiary standards and have not all been revisited with modern large-scale randomized trials, which has made Acthar Gel a frequent subject of discussion among health-policy researchers, insurers, and the FDA itself about how older drugs' indications hold up against today's evidence bar.
An Evidence Gap Worth Understanding
This is a different kind of evidence gap than the one PeptideAAA usually discusses with unapproved research-chemical peptides. Acthar Gel is genuinely FDA-approved and has decades of real-world human use behind it — this isn't a case of animal-only data being extrapolated to humans. The open question is narrower: for some of its older-approved uses, the trial evidence is thinner or older than what would typically be required for a brand-new drug seeking approval for the same condition today. That's a useful reminder that "FDA-approved" describes a regulatory status, not a single fixed level of evidence quality — the strength of evidence behind an approval can vary significantly by indication and by when that indication was added to the label.
Safety Considerations
Because Acthar Gel works largely by raising cortisol, its side-effect profile overlaps with other corticosteroid therapies: increased infection risk from immune suppression, effects on blood sugar and blood pressure, mood changes, and the potential for the body's own adrenal hormone production to become suppressed with prolonged use. It also carries contraindications related to its porcine origin and other standard corticosteroid precautions. As with any corticosteroid-class therapy, decisions about starting, stopping, or adjusting treatment should be made with a prescribing physician who can weigh the specific condition being treated against these risks.
Regulatory Status
Acthar Gel is an FDA-approved prescription drug, available only through a licensed prescriber — not a research chemical, supplement, or self-sourced product. Its high list price and the ongoing evidence debate around some of its indications have drawn scrutiny from insurers and policymakers, but that is a reimbursement and evidence-quality conversation, not a question about its regulatory status, which has remained FDA-approved throughout.