Dydrogesterone

Dydrogesterone was designed to behave like the progesterone the ovaries release after ovulation, which prepares and then maintains the lining of the womb. Several other progestogens also have some oestrogen-like, androgen-like or corticosteroid-like action; this one does not. Women on HRT who still have a uterus need a progestogen as well as oestrogen, since oestrogen alone would thicken the lining, and dydrogesterone keeps that in check.

Six problems appear: painful periods, endometriosis, irregular cycles, periods that have stopped because of a hormonal fault, heavy or erratic bleeding with no structural cause, and premenstrual syndrome. HRT is a seventh setting, where an oestrogen is taken with it. Each has its own timetable, so no single pack size fits every use.

Packs hold 10, 30, 40 or 60. Suppose twice-daily treatment runs from day 5 to day 25: that needs 42 tablets, and a pack of 40 would leave the last day short by two. Because the stock is imported and generic, its carton and leaflet may be designed for a different market, so look at the strip and confirm the name and the 10 mg strength before swallowing any tablet. A pharmacist can help to work out how many tablets a planned course will use.

Every schedule is counted from the first day of proper bleeding. For painful periods one 10 mg tablet is taken morning and evening between days 5 and 25. Endometriosis uses 10 mg two or three times a day, on the same days or all the way through the cycle. When cycles are irregular or periods are absent, twice-daily tablets run from day 11 to day 25, with an oestrogen as well if there is no bleeding. In PMS the days shift to 12 through 26. HRT is different again: with continuous oestrogen, 10 mg daily is added for the last 14 days of the 28-day cycle, while with cyclical oestrogen it covers the final 12 to 14 days. For HRT, the dose may be increased to 20 mg daily depending on the clinical response. Many prescribers like patients to note the first day of each bleed, its heaviness, any spotting and pain, so that treatment days can be adjusted.

Contraindications include allergy to its ingredients, known or suspected progestogen-dependent tumours, current or previous meningioma, unexplained vaginal bleeding, severe acute or chronic liver disease, bile pigment metabolism disorders, current or previous liver tumours, thrombophlebitis and thromboembolic disease; oestrogen contraindications also apply when the medicines are combined. Drugs that quicken the liver’s metabolism can undermine its action, and the SmPC singles out St John’s wort, phenobarbital, phenytoin, carbamazepine, rifampicin, rifabutin, nevirapine and efavirenz. Breastfeeding mothers should not take it, since neither the amount reaching milk nor the effect on the baby is known. Tell the prescriber about all other medicines, herbal ones included.

Common side effects include headache, migraine, nausea, tender breasts and changes in menstrual bleeding, including spotting between periods. Rarer reactions include dizziness, low mood, vomiting, a rash and added weight. A severe sudden headache resembling migraine, or a sudden change in vision, means the tablets should be stopped and medical advice sought without delay. Persistent bleeding warrants a check as well. If a reaction is suspected, it can be reported online through the MHRA Yellow Card scheme.

Dydrogesterone alone is licensed in Britain as Nalvee 10 mg film-coated tablets. Products that join it to oestrogen for HRT, Femoston among them, are also prescription-only. Your doctor decides whether Dydrogesterone is right for you, at what dose and on which days.