1. Clinical Overview
Progesterone (Natural Micronized) 300mg is a bioidentical hormone preparation used primarily for hormone replacement therapy (HRT) and luteal phase support. The micronization process enhances its oral bioavailability by reducing particle size, allowing for effective absorption despite significant first-pass metabolism. It is a key hormone in the menstrual cycle and pregnancy, opposing estrogen's effects on the endometrium.
| Onset | Duration | Bioavailability |
|---|---|---|
| Oral: 1-2 hours for peak plasma concentration. Vaginal: Variable, with systemic effects observed within hours but local endometrial effects are primary. | Approximately 24 hours, necessitating once-daily or twice-daily dosing for sustained effect. | Oral: <10% due to extensive first-pass hepatic metabolism. Vaginal: Variable systemic absorption; primarily acts locally on endometrium. |
2. Mechanism of Action
Progesterone is the primary endogenous progestogen. It transforms a proliferative endometrium (stimulated by estrogen) into a secretory one, suitable for implantation. It maintains pregnancy by suppressing uterine contractility and maternal immune response. It also exerts negative feedback on the hypothalamic-pituitary axis, inhibiting gonadotropin secretion.
3. Indications & Uses
- Secondary Amenorrhea
- Luteal Phase Support in Assisted Reproductive Technology (ART)
- Hormone Replacement Therapy (HRT) in postmenopausal women with an intact uterus (to oppose estrogen and prevent endometrial hyperplasia)
4. Dosage & Administration
Adult Dosage: **Secondary Amenorrhea:** 400 mg orally daily at bedtime for 10 days. **HRT (Sequential):** 200 mg orally daily for the last 12-14 days of each estrogen cycle. **HRT (Continuous Combined):** 100-200 mg orally daily continuously with estrogen. **Luteal Phase Support (ART):** 200-800 mg per day vaginally or orally, in divided doses, starting after oocyte retrieval and continuing for up to 10-12 weeks of pregnancy. **PMS/PMDD:** 200-400 mg orally daily at bedtime, cyclically.
Administration: **Oral:** Take at bedtime to minimize dizziness/drowsiness. Can be taken with or without food, but taking with food may enhance bioavailability. Swallow capsule whole. **Vaginal:** Insert deeply into the vagina as per prescribed schedule, usually once or twice daily. Lie down for some time after insertion. Wash hands before and after.
5. Side Effects
Common side effects may include:
- Drowsiness, somnolence
- Dizziness
- Headache
- Breast tenderness
- Abdominal bloating/cramping
- Mood swings
- Breakthrough bleeding/spotting
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Ketoconazole, Itraconazole, Clarithromycin | Inhibit CYP3A4, increasing progesterone levels and risk of side effects. | Major |
| Rifampicin, Carbamazepine, Phenytoin, St. John's Wort | Induce CYP3A4, decreasing progesterone efficacy. | Major |
| Other CNS Depressants (Alcohol, Benzodiazepines, Opioids) | Additive sedative effect, increased drowsiness and dizziness. | Moderate |
| Drugs affecting liver enzymes (e.g., HIV protease inhibitors) | May alter progesterone metabolism. | Moderate |
7. Patient Counselling
- DO take the medication exactly as prescribed, at the same time each day.
- DO take oral capsules at bedtime if drowsiness occurs.
- DO use a calendar or reminder for cyclic therapy.
- DO report any unusual vaginal bleeding immediately.
- DONT stop taking the medication abruptly without consulting your doctor.
- DONT take with grapefruit juice without consulting your doctor.
- DONT use if you are pregnant (except under specific fertility treatment guidance).
8. Toxicology & Storage
Overdose: Acute overdose may lead to severe drowsiness, dizziness, nausea, vomiting, and lethargy. No specific life-threatening symptoms reported at typical doses.
Storage: Store at room temperature (15-25°C), protected from light and moisture. Keep out of reach of children. Do not use after the expiry date printed on the pack.