Dydrogesterone

What it is

Dydrogesterone is a synthetic progestogen, a laboratory-made analogue of the body's own progesterone. It acts on progesterone receptors in the lining of the womb, opposing the growth-promoting effect of oestrogen there. It is prescription-only, used in conditions of progesterone deficiency and as the progestogen part of menopausal hormone therapy, where it protects the endometrium in women taking oestrogen.

Used for

• Menopause

What to know while taking it

The tablets can be taken with or without food, so the practical question is not what they are eaten with but keeping to the pattern of days the doctor set out, since the endometrial protection depends on the timing rather than on any single tablet. Breakthrough bleeding or spotting is common in the first months of hormone therapy and usually settles. Because this is one half of a hormone regimen, it is not a drug to pause or restart independently of the oestrogen it accompanies.

When to see a doctor

Bleeding that is heavy, or that starts again after the pattern had settled, should be looked at rather than waited out. Sudden severe headache, chest pain, breathlessness, or pain and swelling in one leg during hormone therapy means see a doctor without delay.