Progesterone and is responsible for approximately 70% of cytochrome P450-mediated progesterone metabolism. Other routes include 6α-, 16α-, and 16β-hydroxylation. However, treatment of women with ketoconazole, a strong CYP3A4 inhibitor, had minimal effects on progesterone levels, producing only a slight and non-significant increase, and this suggests that cytochrome P450 enzymes play only a small role in progesterone metabolism. In women, progesterone levels are relatively low during the preovulatory phase of the menstrual cycle, rise after ovulation, and are elevated during the luteal phase, as shown in diagram below. Progesterone levels tend to be less than 2 ng/mL prior to ovulation, and greater
Pharmacokinetics of progesterone 800 mg/day vaginal progesterone (about 70 ng/mL and 12 ng/mL, respectively), although local progesterone levels in the uterus were 10 times higher with the vaginal route due to a uterine first-pass effect (around 1.5 ng/mL and almost 12 ng/mL, respectively). The duration of progesterone is extended by the intramuscular route due to a depot effect in which it is stored locally in adipose tissue, and can be administered once every 1 to 3 days. The half-life of intramuscular progesterone is significantly longer when it is injected into the gluteal muscles of the buttocks rather than the deltoid muscle of the