ALLYLESTRENOL

Allylestrenol is a synthetic progestogen used in obstetrics to support pregnancy, particularly in patients with a history of miscarriage, preterm labour, or intrauterine growth restriction (IUGR). It mimics the action of natural progesterone, the hormone responsible for maintaining pregnancy by promoting a stable uterine environment and preventing early contractions. Allylestrenol has a low androgenic profile, making it safe for maternal and fetal health when used appropriately. Developed in the 1960s, allylestrenol has been widely used in several countries, including India and Japan, for the prevention of pregnancy-related complications. Though not FDA-approved in the United States, it is included in treatment protocols across many parts of Asia and Europe. In India, it is prescribed within gynaecology and high-risk obstetrics care, particularly for patients with a history of threatened abortion or hormone-related pregnancy loss. It is available in oral tablet form, typically 5 mg strength, for once or twice daily dosing.

Allylestrenol is used for: Preventing threatened and recurrent miscarriage Managing preterm labor and uterine irritability Supporting pregnancies with intrauterine growth restriction (IUGR) Treating habitual abortion caused by luteal phase defects Hormonal support in assisted reproductive techniques (off-label)

Allylestrenol is typically prescribed as a 5 mg oral tablet, taken once or twice daily depending on clinical condition. The duration and dose are determined by the doctor based on pregnancy risk factors and the need for uterine support. It can be taken with or without food and should be used at the same time each day for optimal effectiveness. It is not available in injectable or extended-release formulations. Therapy is often continued through the first trimester or as advised during antenatal care. Discontinuation is usually gradual to avoid hormonal imbalance.

Common side effects: Nausea Headache Dizziness Breast tenderness Bloating Serious side effects (seek medical help): Sudden chest pain or shortness of breath Visual disturbances Severe abdominal pain Swelling or pain in legs (signs of clot) Yellowing of skin or eyes (signs of liver dysfunction)

Do not use if the patient has hormone-sensitive cancers (e.g., breast or uterine cancer). Avoid use in patients with active liver disease, cholestatic jaundice, or undiagnosed vaginal bleeding. Not intended for use in non-pregnancy-related hormonal disorders unless specifically advised. Discontinue immediately if allergic reactions like skin rash, swelling, or breathing difficulty occur. Caution is advised in patients with a history of thromboembolic disorders, as progestins may increase clot risk.

Before starting Allylestrenol, your doctor will evaluate if you have any history of liver problems, blood clots, or hormone-sensitive conditions. Inform your healthcare provider if you’re allergic to any progesterone-based medicines or if you have unusual vaginal bleeding. Though generally considered safe in pregnancy, always take this medicine under supervision. Let your doctor know if you are breastfeeding, planning pregnancy via IVF, or using other hormonal treatments. Routine check-ups, including ultrasound and blood hormone monitoring, may be done during treatment. Do not stop taking medicine abruptly without medical advice. Carry your antenatal medication list with you, especially in emergencies or hospital visits.

Use Allylestrenol only under medical supervision. Regular follow-ups are necessary to monitor pregnancy progression and enable dose adjustments as required. Do not self-medicate or stop the medication abruptly without consulting your doctor. Inform your healthcare provider of all medications you are currently taking, and report any unusual symptoms immediately. This medicine is not a general hormone supplement—it is indicated for specific pregnancy-related conditions.

https://pmc.ncbi.nlm.nih.gov/articles/PMC10500903/ https://precision.fda.gov/uniisearch/srs/unii/i47vb5dz8o https://go.drugbank.com/drugs/DB01431