Estradiol hemihydrate
What is it?
Estradiol hemihydrate is a synthetic form of oestrogen. It is body identical meaning it is like the naturally occuring oestrogen found in your body but has been made in a lab. Estradiol hemihydrate is currently only used in the combined contraceptive pill Zoely. It is also a commonly used ingredient in HRT (hormone replacement therapy) which is used to treat the symptoms of menopause.
Most combined hormonal contraceptives (like the pill, patch and vaginal ring) contain a type of oestrogen called ethinylestradiol, alongside a synthetic progestogen.
How does it work?
Estradiol hemihydrate is a form of estradiol (aka oestrogen), and works with the progestogen in the combined pill to stop ovulation (the release of an egg from the ovaries) which prevents sperm meeting an egg so pregnancy can’t occur. Estradiol also helps to regulate the lining of the womb helping to prevent breakthrough bleeding on the pill.
What is it used in?
Zoely is the only combined pill brand currently available in the UK containing estradiol hemihydrate.
It is used in most types of HRT including:
- Elleste Solo and Elleste Duet
- Femoston and Femoston Conti
- Bijuve
- Estraderm
- Estradot
- Evorel Sequi and Evorel Conti
- Lenzetto
- Sandrena
- Vagifem
What are the side effects?
Possible side effects of estradiol hemihydrate include:
- Bloating
- Breast tenderness or swelling
- Reduced sex drive
- Headaches
- Mood swings
- Nausea or vomiting
- Water retention
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