1. Clinical Overview
Medroxyprogesterone acetate (MPA) is a synthetic derivative of progesterone, a naturally occurring female sex hormone. It is a potent progestin used primarily for secondary amenorrhea, abnormal uterine bleeding, and as part of hormone replacement therapy (HRT). In the Indian context, it is a widely prescribed, cost-effective option for menstrual regulation and endometrial protection.
| Onset | Duration | Bioavailability |
|---|---|---|
| Therapeutic effects on endometrium are typically observed within 24-48 hours. Full therapeutic effect for menstrual regulation may take 3-5 days of therapy. | Approximately 24 hours per oral dose. Its prolonged action on endometrial tissue can last for several days after discontinuation. | Oral bioavailability is nearly complete, approaching 100%. |
2. Mechanism of Action
Medroxyprogesterone acetate transforms proliferative endometrium into secretory endometrium. It inhibits the secretion of pituitary gonadotropins (LH and, to a lesser extent, FSH), preventing follicular maturation and ovulation at higher doses. It also exerts an anti-estrogenic effect on the endometrium, making it useful in treating estrogen-induced endometrial hyperplasia.
3. Indications & Uses
- Secondary Amenorrhea
- Abnormal Uterine Bleeding due to hormonal imbalance (e.g., anovulatory cycles, endometrial hyperplasia without atypia)
4. Dosage & Administration
Adult Dosage: For secondary amenorrhea: 5-10 mg daily for 5-10 days. Bleeding usually occurs within 3-7 days after discontinuation. For abnormal uterine bleeding: 5-10 mg daily for 5-10 days beginning on day 16 or 21 of the cycle. For endometrial protection with estrogen HRT: 10 mg daily for the last 10-14 days of each estrogen cycle.
Administration: Take orally with or without food, preferably at the same time each day. For cyclic therapy, follow the prescribed schedule strictly (e.g., days 16-25 of a 28-day cycle). A calendar may be helpful.
5. Side Effects
Common side effects may include:
- Breakthrough bleeding/spotting
- Amenorrhea (during therapy)
- Menstrual flow changes
- Breast tenderness/pain
- Headache
- Dizziness
- Nausea
- Bloating/abdominal cramps
- Fatigue
- Weight changes
- Acne
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Aminoglutethimide | Decreases MPA levels by inducing hepatic metabolism. | Moderate |
| Rifampicin, Rifabutin | Significantly reduce MPA plasma levels via CYP3A4 induction, potentially reducing efficacy. | Major |
| Phenytoin, Carbamazepine, Phenobarbital | Reduce MPA plasma levels via enzyme induction. | Major |
| Ketoconazole, Itraconazole | May increase MPA levels by inhibiting CYP3A4. | Moderate |
| Warfarin and other Coumarin anticoagulants | MPA may decrease anticoagulant effect; monitor INR closely. | Moderate |
| Insulin, Oral Hypoglycemics | MPA may decrease glucose tolerance; monitor blood glucose. | Moderate |
| Cyclosporine | MPA may inhibit metabolism, increasing cyclosporine levels and toxicity risk. | Moderate |
7. Patient Counselling
- DO take the medicine exactly as prescribed, at the same time each day.
- DO use a non-hormonal contraceptive method (barrier) if sexually active, as this dose is not for birth control.
- DO report any severe headache, chest pain, leg swelling, shortness of breath, or vision changes immediately.
- DONT take if you are pregnant or suspect pregnancy.
- DONT smoke, as it greatly increases the risk of serious cardiovascular side effects.
- DONT start any new medicine (including OTC, herbal like St. John's Wort) without consulting your doctor.
8. Toxicology & Storage
Overdose: Acute oral overdose is unlikely to be life-threatening. Symptoms may include nausea, vomiting, drowsiness, dizziness, and possibly withdrawal bleeding in females. No specific teratogenic effects are expected from a single acute overdose in a non-pregnant woman.
Storage: Store below 30°C. Protect from light and moisture. Keep out of reach of children. Do not use after the expiry date printed on the pack.