Hydroxyprogesterone caproate, also known as 17α-hydroxyprogesterone caproate, is closer to progesterone in terms of structure and pharmacology than most other progestins, and is essentially a pure progestogen – that is, a selective agonist of the progesterone receptor (PR) with minimal or no other hormonal activity. However, hydroxyprogesterone caproate has improved pharmacokinetics compared to progesterone, namely a much longer duration with intramuscular injection in oil solution.
