Although the elimination half-life of intramuscular OHPC in oil solution in non-pregnant women is about 8 days, the elimination half-life of intramuscular medroxyprogesterone acetate in microcrystalline aqueous suspension in women is around 50 days. OHPC is also to some degree less potent than the more closely related ester hydroxyprogesterone acetate (OHPA; 17α-hydroxyprogesterone acetate).17α-Hydroxyprogesterone (OHP) has weak progestogenic activity, but C17α esterification results in higher progestogenic activity. Of a variety of different esters, the caproate (hexanoate) ester was found to have the strongest progestogenic activity, and this served as the basis for the development of OHPC, as well as other caproate progestogen esters such as gestonorone caproate. OHPC is a much more potent progestogen than 17α-hydroxyprogesterone, but does not have as high of affinity for the PR as progesterone. OHPC has about 26% and 30% of the affinity of progesterone for the human PR-A and PR-B, respectively. The medication was no more efficacious than progesterone in activating these receptors and eliciting associated gene expression in vitro. Antigonadotropic effects
Due to activation of the PR, OHPC has antigonadotropic effects, or produces suppression of the hypothalamic–pituitary–gonadal axis, and can significantly suppress gonadotropin secretion and gonadal sex hormone production at sufficiently high doses. One study found that OHPC by intramuscular injection at a dosage of 200 mg twice weekly for the first two weeks and then 200 mg once weekly for 12 weeks did not significantly influence urinary excretion of estrogens, luteinizing hormone, or follicle-stimulating hormone in men with benign prostatic hyperplasia.
Hydroxyprogesterone caproate (OHPC), sold under the brand names Proluton and Makena among others, is a progestin medication which is used to prevent preterm birth in pregnant women with a history of the condition and to treat gynecological disorders. It has also been formulated in combination with estrogens for various indications (brand names Gravibinon and Primosiston) and as a form of long-lasting injectable birth control (brand name Chinese Injectable No. 1). It is not used by mouth and is instead given by injection into muscle or fat, typically once per week to once per month depending on the indication.OHPC is generally well tolerated and produces few side effects. Injection site reactions such as pain and swelling are the most common side effect of OHPC. The medication may increase the risk of gestational diabetes when used in pregnant women. OHPC is a progestin, or a synthetic progestogen, and hence is an agonist of the progesterone receptor, the biological target of progestogens like progesterone. It has some antimineralocorticoid activity and no other important hormonal activity. The medication shows a number of differences from natural progesterone.OHPC was discovered in 1953 and was introduced for medical use in 1954 or 1955. It was marketed in the United States under the brand name Delalutin and throughout Europe under the brand name Proluton. The medication was discontinued in the United States in 1999. However, OHPC was subsequently reintroduced in the United States under the brand name Makena for the treatment of preterm birth in 2011.