1. Clinical Overview
Allylestrenol is a synthetic, orally active progestogen hormone used primarily in obstetrics and gynecology. It is a derivative of progesterone with potent progestational activity and weak androgenic effects. In the Indian context, it is a well-established, cost-effective agent for the prevention of recurrent miscarriage and the treatment of threatened abortion, particularly in patients with a history of luteal phase defect or progesterone deficiency.
| Onset | Duration | Bioavailability |
|---|---|---|
| Clinical effects on uterine quiescence are typically observed within 24-48 hours of administration. | The therapeutic effect is sustained for approximately 24 hours, necessitating once or twice-daily dosing. | Approximately 70-80% after oral administration. |
2. Mechanism of Action
Allylestrenol binds to intracellular progesterone receptors in the uterus, fallopian tubes, vagina, and breast tissue. This receptor-hormone complex translocates to the nucleus, binds to DNA, and modulates gene transcription. The primary therapeutic effect in obstetrics is the transformation of the endometrium from a proliferative to a secretory state, creating a favorable environment for implantation and maintenance of pregnancy. It also directly inhibits uterine contractility by decreasing the sensitivity of the myometrium to oxytocin and prostaglandins, promoting uterine quiescence.
3. Indications & Uses
- Prevention of habitual (recurrent) abortion
- Treatment of threatened abortion
4. Dosage & Administration
Adult Dosage: For threatened abortion: 5 mg three times daily until symptoms cease for 5-7 days, then 5 mg twice daily for 1 week, then 5 mg once daily until 12-16 weeks of gestation. For habitual abortion: 5 mg once or twice daily, starting as soon as pregnancy is confirmed, continued until at least 12-16 weeks of gestation or longer as advised.
Administration: Oral administration. Can be taken with or without food. Tablet should be swallowed whole with a glass of water. For pregnancy-related indications, dosage must be strictly adhered to as per obstetrician's advice. Do not stop abruptly if used for pregnancy support; taper as directed.
5. Side Effects
Common side effects may include:
- Nausea
- Drowsiness/sedation
- Breast tenderness
- Weight gain
- Headache
- Edema/fluid retention
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Rifampicin | Induces hepatic metabolism of allylestrenol, reducing its efficacy. | Major |
| Carbamazepine, Phenytoin, Phenobarbital | Enzyme inducers; may decrease allylestrenol levels. | Major |
| Ketoconazole, Itraconazole | Potent CYP3A4 inhibitors; may increase allylestrenol levels and risk of side effects. | Moderate |
| Warfarin and other Coumarin anticoagulants | Allylestrenol may reduce anticoagulant effect; monitor INR closely. | Major |
| Insulin, Oral Hypoglycemics | Allylestrenol may decrease glucose tolerance, requiring dose adjustment. | Moderate |
| Antihypertensives | Effect may be reduced due to fluid retention. | Moderate |
| Cyclosporine | Allylestrenol may inhibit metabolism, increasing cyclosporine toxicity. | Moderate |
7. Patient Counselling
- DO take the medication exactly as prescribed by your doctor. Do not change the dose or stop suddenly, especially during pregnancy.
- DO inform all your doctors and dentists that you are taking this medicine before any treatment.
- DO report any unusual vaginal bleeding, severe headache, visual changes, chest pain, shortness of breath, leg pain/swelling, or severe mood changes immediately.
- DONT take this medicine if you are pregnant for an unapproved indication without consulting your obstetrician.
- DONT take other medicines, including herbal supplements, without informing your doctor.
8. Toxicology & Storage
Overdose: Acute overdose may manifest as severe nausea, vomiting, drowsiness, dizziness, and possibly withdrawal bleeding in women. No specific life-threatening symptoms are reported at extremely high doses.
Storage: Store below 30°C, in a cool, dry place, protected from light and moisture. Keep the container tightly closed. Keep out of reach of children. Do not use after the expiry date printed on the pack.