Medroxyprogesterone Acetate: Effects & Uses
Medroxyprogesterone acetate (MPA) is a synthetic progestogen used in hormone therapy, contraception, and the treatment of hormone-dependent conditions.
Things worth knowing about "Medroxyprogesterone acetate"
Medroxyprogesterone acetate (MPA) is a synthetic progestogen used in hormone therapy, contraception, and the treatment of hormone-dependent conditions.
What is Medroxyprogesterone Acetate?
Medroxyprogesterone acetate (abbreviated MPA) is a synthetic progestogen -- an artificial hormone that closely resembles the natural hormone progesterone. It belongs to the class of progestogens (progesterone derivatives) and has been used in medicine for decades. MPA is available in several forms: as oral tablets, as a depot injection, and as a component of combined hormonal preparations.
Indications (Medical Uses)
Medroxyprogesterone acetate is used for a variety of medical purposes:
- Hormonal contraception: As a depot injection (e.g., Depo-Provera®) administered every three months to prevent pregnancy
- Menstrual disorders: Treatment of irregular or absent menstrual periods (amenorrhea, dysmenorrhea)
- Endometriosis: Relief of symptoms caused by abnormal growth of uterine lining tissue outside the uterus
- Hormone replacement therapy (HRT): Combined with estrogens to protect the uterine lining in postmenopausal women
- Endometrial carcinoma: As part of palliative treatment for cancer of the uterine lining
- Breast cancer: Used in certain advanced or metastatic cases
- Androgen deprivation: Used to reduce libido in paraphilic disorders or as part of treatment for prostate cancer
Mechanism of Action
MPA works primarily by binding to progesterone receptors in various tissues. The main mechanisms of action are:
- Inhibition of ovulation: MPA suppresses the release of LH (luteinizing hormone) and FSH (follicle-stimulating hormone) from the pituitary gland, thereby preventing ovulation.
- Alteration of the uterine lining: MPA transforms the endometrium into a secretory state, making it difficult for a fertilized egg to implant.
- Thickening of cervical mucus: The mucus at the cervix becomes thicker, making it harder for sperm to penetrate.
- Antiandrogenic effect: At higher doses, MPA inhibits the production and action of male sex hormones (androgens).
- Antiproliferative effect: In cancer therapy, MPA inhibits the growth of hormone-dependent tumor cells.
Dosage and Usage Notes
The dosage of medroxyprogesterone acetate depends strongly on the indication:
- Depot injection for contraception: 150 mg every 12 weeks (3 months) intramuscularly or 104 mg subcutaneously
- Oral use for menstrual disorders: Usually 5–10 mg daily for 5–10 days
- Hormone replacement therapy: 2.5–10 mg daily or cyclically in combination with estrogens
- Tumor treatment: Higher doses of 200–1000 mg daily, depending on the treatment protocol
Administration should always take place under medical supervision. Self-medication is not recommended.
Side Effects
Like all hormones, medroxyprogesterone acetate can cause side effects. These may vary depending on dose, route of administration, and individual response:
Common Side Effects
- Irregular bleeding or absence of menstruation (amenorrhea)
- Weight gain
- Headaches
- Mood changes, depressive episodes
- Decreased libido (reduced sex drive)
- Breast tenderness or breast pain
Less Common but Serious Side Effects
- Decreased bone density: Especially with long-term use of the depot injection, bone density may decrease, increasing the risk of osteoporosis.
- Thrombosis and embolism: Increased risk of blood clots in veins and arteries
- Cardiovascular risks: May increase the risk of heart disease and stroke
- Breast cancer: Slightly increased risk with long-term use in combined hormone replacement therapy
- Delayed return of fertility after discontinuing the depot injection
Contraindications
MPA must not be used in cases of:
- Known or suspected estrogen- or progesterone-dependent tumors
- Unexplained vaginal bleeding
- Current or previous deep vein thrombosis or pulmonary embolism
- Active or previous arterial cardiovascular disease (e.g., heart attack, stroke)
- Severe liver disease or liver tumors
- Pregnancy
- Known hypersensitivity to MPA or any of the excipients
Drug Interactions
Medroxyprogesterone acetate can interact with several medications:
- Enzyme inducers (e.g., rifampicin, phenytoin, carbamazepine, St. John's Wort) can accelerate the breakdown of MPA and reduce its effectiveness.
- Aminoglutethimide can significantly reduce the availability of MPA in the bloodstream.
- Interactions with anticoagulants (blood thinners) and antidiabetic medications are possible.
References
- European Medicines Agency (EMA): Product information for medroxyprogesterone acetate-containing preparations. Available at: www.ema.europa.eu
- World Health Organization (WHO): Medical Eligibility Criteria for Contraceptive Use, 5th edition. Geneva: WHO, 2015.
- Sitruk-Ware R.: Pharmacological profile of progestins. Maturitas 2008; 61(1-2): 151–157. DOI: 10.1016/j.maturitas.2008.11.011
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