The long-term administration produces the same effects as those produced by cortisone, cortisol and their synthetic analogues. Therefore, therapy may be maintained with less frequent administration. The complex results in a product whose absorption in man is effected over a longer period of time as compared to corticotropin. Synacthen Depot, a long-acting synthetic b1-24-corticotropin, exhibits the same activity as natural ACTH with regard to all its biological activities. It also has some degree of melanotropic activity and lipolytic effect.

In addition to controlling corticosteroid secretion, ACTH also increases the synthesis and release of the other adrenal steroids, namely aldosterone and the adrenal androgens. In its absence, adrenal blood flow is diminished, adrenal atrophy invariably ensues and cortisol secretion is markedly reduced. The most important physiological effects of ACTH involve the adrenal cortex and include the maintenance of adrenal weight and the control of adrenal corticosteroid synthesis and release. In contrast, the N terminal 24 amino-acid sequence is common to all species and is relatively non-antigenic, and it is only these amino-acids which are involved in its biological activities.:

The sequence of amino-acid occupying positions 25 to 33 varies among species and it is this part of the molecule which is most antigenic when ACTH of foreign origin is administered to man. Natural adrenocorticotropin is a straight-chain polypeptide containing 39 amino acids which, by convention, are numbered from the N terminal end of the molecule.

Synacthen atc4