The Sound of Evolution
Medroxyprogesterone acetate
Mechanism of action:
Medroxyprogesterone acetate is a synthetic progestin and an acetate derivative of progesterone. After binding to intracellular progesterone receptors, Medroxyprogesterone acetate forms a ligand-receptor complex that enters the nucleus and regulates the transcription of specific genes, producing physiological responses similar to those of the luteal phase. Medroxyprogesterone acetate also exerts negative feedback on the hypothalamus and pituitary gland, suppressing the secretion of gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH). This prevents the LH surge and thereby inhibits ovulation.
Reference(s):
1. Akpoviroro JO et al. (1981). Binding of the contraceptive steroids medroxyprogesterone acetate and ethynyloestradiol in blood of various species. J Steroid Biochem.
2. Johansson ED et al. (1986). Medroxyprogesterone acetate pharmacokinetics following oral high-dose administration in humans: a bioavailability evaluation of a new MPA tablet formulation. Acta Pharmacol Toxicol (Copenh).
3. Sierra-Ramirez JA et al. (2011). Comparative pharmacokinetics and pharmacodynamics after subcutaneous and intramuscular administration of medroxyprogesterone acetate (25 mg) and estradiol cypionate (5 mg). Contraception.