• Molecular Formula:C₂₇H₄₀O₄
• Molecular Weight: 428.61
• CAS Registry Number: 630-56-8
• Synonyms:17a-Hydroxyprogesterone caproate; 17a-Hydroxy-4-pregnene-3,20-dione caproate

Hydroxyprogesterone caproate is a progestogen structurally related to progesterone that has been used for recurrent miscarriage and various menstrual disorders. In recurrent miscarriage associated with proven progesterone deficiency, doses of 250 to 500 mg weekly by intramuscular injection have been given during the first half of pregnancy. Hydroxyprogesterone caproate has also been used to prevent premature labour (see below). The acetate and the enantate have also been used.

PROGESTERONE is most effective when administered parenterally and it is rather rapidly metabolized and excreted. In order to avoid daily injections of progesterone, it is necessary to have either a parenteral form with a prolonged effect (1, 2) or an oral substance with progestational properties. The progestational substance most widely used for oral administration is 20,21-antrydro-17-β-hydroxyprogesterone (pregneninolone, 17--ethinyltestosterone).

It is the purpose of this paper to introduce and describe a new steroid for oral administration, 17--hydroxyprogesterone acetate*, and to compare it with the most widely used oral substance with progestational properties, 20,21-anhydro-17-β-hydroxyprogesterone.