Ethinylestradiol

Key facts

• Ethinylestradiol is a synthetic estrogen, the estrogen component of most combined oral contraceptive pills, always paired with a progestogen.
• It is taken daily, usually with a hormone-free or placebo interval, at roughly the same time each day for reliable contraception.
• It raises the risk of venous blood clots, stroke and heart attack. This risk is markedly higher in women who smoke and are over 35, and increases further with obesity, immobility and age.
• Never take it unopposed, without a progestogen, if you still have a uterus, since estrogen alone thickens the womb lining and raises the risk of endometrial cancer.
• Seek urgent care for leg pain or swelling, sudden breathlessness, chest pain, or a sudden severe headache or vision change.

What ethinylestradiol treats

Ethinylestradiol, combined with a progestogen, is used for contraception. Some combined preparations are also used to regulate irregular cycles or reduce heavy or painful periods. It is not used as a stand-alone estrogen replacement for menopause; conjugated oestrogens and similar products fill that role instead.

How ethinylestradiol works

Combined with a progestogen, ethinylestradiol suppresses the pituitary hormones that trigger ovulation, thickens cervical mucus so sperm cannot easily pass through, and thins the lining of the womb. Together these effects prevent pregnancy.

Before you take it

• Do not take it if you smoke and are over 35, have a personal or strong family history of blood clots, migraine with aura, uncontrolled high blood pressure, certain liver diseases, or known or suspected breast or endometrial cancer.
• Tell your prescriber about any history of stroke, heart attack, clotting disorders, or planned major surgery, since combined contraceptives are usually stopped in advance of prolonged immobility.
• Some medicines, including rifampicin and certain anti-epileptics, reduce its contraceptive effectiveness, so additional contraception may be needed.

Side effects

Common effects include nausea, breast tenderness, headache, breakthrough bleeding, and mood changes.

Stop and seek urgent medical care for any of these, the recognised warning signs of a clot, stroke or heart attack:

• Leg pain or swelling.
• Sudden chest pain or breathlessness.
• Sudden severe headache, vision disturbance, or weakness on one side of the body.

Safety essentials

• The clot, stroke and heart attack risk is the defining safety issue with this medicine. If you smoke, stopping matters more than with almost any other drug decision, and you should tell every prescriber, dentist and surgeon that you take a combined hormonal contraceptive before any operation or period of prolonged immobility.
• Never take estrogen alone if your uterus is intact; a progestogen must be added to protect the womb lining, since unopposed estrogen raises endometrial cancer risk.
• If you miss pills, vomit, or have diarrhoea, follow the missed-pill instructions for your specific product and use additional contraception as advised.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.