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Inhibits (at the usual dose range) the secretion of pituitary gonadotropins, which in turn prevents follicular maturation and ovulation.
Pharmacokinetics and Metabolism
Absorption: After intramuscular administration of 10 mg of progesterone in oil maximum plasma concentrations (geometric mean of 7 ng/mL) were reached within approximately 8 hours after injection and plasma concentrations remained above baseline for about 24 hours after injection. Injection of 10, 25, and 50 mg resulted in geometric mean values for maximum plasma concentration (CMAX) of 7, 28, and 50 ng/mL, respectively.
Distribution: Progesterone is extensively bound to plasma proteins, primarily albumin (50-54%) and cortisol-binding protein (43-48%).
Metabolism: Progesterone is metabolized primarily in the liver by reduction to pregnanediol, pregnanetriol and pregnanolone. Subsequent conjugation results in the formation of glucuronide and sulfate metabolites. The mean plasma metabolic clearance rate in cycling women is 2510 ± 135 (SEM) L/day.
Excretion: The glucuronide and sulfate conjugates of pregnanediol and pregnanolone are excreted in the urine and bile. Progesterone metabolites which are excreted in the bile may undergo enterohepatic recycling or may be excreted in the feces.
The pharmacokinetic data was determined in a small number of patients, limiting the precision in which population values may be estimated.
Renal Insufficiency: The safety and effectiveness in patients with renal insufficiency have not been established. Since progesterone metabolites are excreted mainly by the kidneys, progesterone should be administered with caution and careful monitoring in this patient population (see PRECAUTIONS).
Hepatic Insufficiency: The safety and effectiveness in patients with hepatic insufficiency have not been established. Since progesterone is metabolized by the liver, use in patients with liver dysfunction or disease is contraindicated (see CONTRAINDICATIONS).
The metabolism of progesterone by human liver microsomes was inhibited by ketoconazole (IC50 < 01 ÁM). Ketoconazole is a known inhibitor of cytochrome P450 3A4 and these data suggest that ketoconazole or other known inhibitors of this enzyme may increase the bioavailability of progesterone. The clinical relevance of the in vitro findings is unknown.
Last reviewed on RxList: 2/20/2008
This monograph has been modified to include the generic and brand name in many instances.
Additional Progesterone Injection Information
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