Norethisterone is a synthetic form of the female hormone progesterone. Doctors prescribe norethisterone to treat irregular or painful menstration, premenstrual syndrome and endometriosis. It also can be used to postpone menstruation for special circumstances. High doses are prescribed to treat breast cancer.
Hormonal Side Effects
The most common norethisterone side effects, experienced by fewer than one in 10 women, include breakthrough bleeding, breast tenderness, changes in sex drive, excessive hair growth, fluid retention and bloating and hair loss.
Additional Side Effects
Additional common side effects include depressed mood, dizziness, drowsiness, fatigue, headaches, insomnia and nausea, rash and itching, and weight gain.
Progesterone is associated with a slightly-increased risk of blood clots when included with estrogen in oral contraceptives. Progesterone alone may also increase this risk. The risk of blood clots can be increased when people are immobile for long periods of time, such as during bed rest after surgery.
Norethisterone can increase blood sugar levels, and should be taken cautiously by women with diabetes.
Rarely, norethisterone is associated with liver problems. Signs are nausea and vomiting, fatigue, dark urine and jaundice.