 The pharmacokinetics of OHPA have been reviewed.A single intramuscular injection of 150 to 350 mg OHPA in microcrystalline aqueous suspension has been found to have a duration of action of 9 to 16 days in terms of clinical biological effect in the uterus in women.OHPA, also known as 17α-hydroxyprogesterone acetate or as 17α-acetoxypregn-4-ene-3,20-dione, is a synthetic pregnane steroid and a derivative of progesterone.