Corticotropin

In plain language

Corticotropin is purified ACTH from pig pituitary glands, sold as H.P. Acthar Gel, one of the oldest medicines still on the market (approved 1952). It is used for infantile spasms, multiple sclerosis flares and certain rheumatic conditions.

It is the full 39-amino-acid hormone, delivered in a gel that slows absorption so its effect lasts hours. It is also one of the most expensive drugs in the United States per unit of treatment, which has made it a case study in drug pricing.

For students

H.P. Acthar Gel is porcine pituitary ACTH (39 residues, about 4,541 Da for the natural sequence) in a 16% gelatin vehicle providing depot-style absorption after intramuscular or subcutaneous injection. Approved in 1952, it predates the modern randomized-trial era for many of its uses.

Its modern indications rest on a mixed evidence base: infantile spasms (where ACTH is a first-line therapy with the strongest data, versus oral steroids), acute exacerbations of multiple sclerosis (legacy), and certain rheumatic and nephrotic conditions. Acthar is also used off-label or per label in myasthenia gravis and sarcoidosis scenarios. The pricing history (from about 40 dollars per vial in the 1990s to tens of thousands after successive ownership changes) is taught in health economics as a pure pricing-power case, since the molecule is old, natural and inexpensive to make.

For researchers and instructors

Biochemistry. ACTH's full sequence includes regions shared with alpha-MSH (ACTH 1-13 is MSH), explaining melanocyte-stimulating side effects like skin darkening, and the molecule's 39 residues are preserved across species with only position 31 varying (porcine versus human).

Pharmacology. Gel-based depot absorption gives about 12-hour pharmacodynamic effects; dosing is 80 units twice weekly to 80 units daily depending on indication; adverse effects are those of systemic steroid excess (cushingoid features, hyperglycemia, hypertension, adrenal suppression on withdrawal).

Human evidence. A randomized controlled trial (the 2004 United Kingdom Infantile Spasms Study, UKISS) compared ACTH versus prednisolone and vigabatrin, establishing ACTH's first-line role in infantile spasms; for most other uses, evidence predates modern trial standards, a teaching point in itself.

Teaching point. A living museum of pharmaceutical history (animal-derived, pre-trial-era, price-controversial) that still holds a legitimate first-line indication in infantile spasms.