However, a novel oral formulation of OHPC (developmental code name LPCN-1107) is under development and has been found to be effective, though it required administration twice a day in a clinical study.A depot effect occurs when OHPC is injected intramuscularly or subcutaneously, such that the medication has a prolonged duration of action. Following a single intramuscular injection of 1,000 mg OHPC in five women with endometrial cancer, peak levels of OHPC were 27.8 ± 5.3 ng/mL and the time to peak concentrations was 4.6 ± 1.7 (3–7) days. Following 13 weeks of continuous administration of 1,000 mg OHPC per week, trough levels of OHPC were 60.0 ± 14 ng/mL. The pharmacokinetic parameters of 250 mg OHPC once per week by intramuscular injection have also been studied in pregnant women with singleton and multiple (twin and triplet) gestation. Steady state levels of the medication are achieved within 4 to 12 weeks of administration in pregnant women. The duration of clinical biological effect of OHPC by intramuscular injection has also been studied in women. A single intramuscular injection of 65 to 500 mg OHPC in oil solution has been found to have a duration of action of 5 to 21 days in terms of effect in the uterus and on body temperature in women.OHPC has been found to possess similar pharmacokinetics, including peak levels, time to peak levels, area-under-the-curve levels (i.e., total exposure), and elimination half-life, with administration via intramuscular injection or subcutaneous autoinjection.
In contrast to progesterone, OHPC is not metabolized by traditional steroid-transforming enzymes and instead is metabolized exclusively via oxidation at the caproate side chain by cytochrome P450 enzymes. As such, it is not thought to have the same tissue-specific activation and inactivation patterns that progesterone does nor the same non-genomic actions that progesterone and its metabolites possess.Further clinical research is anticipated to provide additional data to help clarify the issue of safety with OHPC. In any case, it has been recommended by the American College of Obstetricians and Gynecologists that pregnant women treated with OHPC receive counseling about its risks and benefits. Pharmacokinetics
Absorption
In animals, the bioavailability of OHPC with intramuscular injection is nearly 100%, but its oral bioavailability is very low at less than 3%. In women, 70 mg/day oral OHPC has similar endometrial potency as 70 mg/day oral OHPA and 2.5 mg/day oral medroxyprogesterone acetate, indicating that oral OHPC and OHPA have almost 30-fold lower potency than medroxyprogesterone acetate via oral administration. Studies on progestogenic endometrial changes with oral OHPC in women are mixed however, with one finding weak effects with 100 mg/day whereas another found that doses of 250 to 1,000 mg produced no effects. As a result of its low oral potency, OHPC has not been used by the oral route and has instead been administered by intramuscular injection.