Norethisterone is relatively new (it certainly was not available to people in ancient times) and was created in 1951 by chemists working for the pharmaceutical company Syntex in Mexico City. It is a progestin, which is a synthetic version of progestogen which is created naturally in the ovaries and placenta.

Before a monthly period, there is a decrease in progestogens in the body. If there is a pronounced decrease then the lining of the uterus is shed during that menstrual period. Norethisterone helps sustain the lining of the uterus until the tablet is stopped. In short, it balances the hormones.

Low doses of Norethisterone act as a hormone replacement therapy or HRT) and to prevent pregnancy. Medium-strength tablets or doses can be used to treat heavy periods (known as menorrhagia). High-strength tablets are sometimes used to treat breast cancer or other female cancers.

Norethisterone was originally used as a form of birth control and was among the earliest birth control pills in the 1960s. Since then, there are many more uses. In the United Kingdom, there are about 800,000 prescriptions made each year for its non-contraceptive uses. If this ratio is applicable in the United States(where it is solder under the name norethinderone) then that means almost 4 million prescriptions each year for its therapeutic (i.e., non-contraceptive) use. Such uses include:

1) to postpone menstruation for upto 3 weeks.
2) to treat irregular and painful menstruation.
3) to treat endometriosis (a painful situation in which the tissue that usually lines the womb grows outside of the womb, instead)
4) to delay a period
5) for premenstrual tension (more commonly known as PMS or PMT).
6) heavy bleeding from the womb (not necessarily related to a heavy period)
7) heavy bleeding during a period
8) painful periods
9) and heavy doses can be used to treat breast cancer

Of course, your doctor and pharmacist will give you more specific and pertinent directions but in general, (and especially for use in birth control) you ought to take the first tablet (usually 5mg) on the first day of your next period. If this is indeed being used for birth control, then for the first two weeks take additional precautions (such as the use of a condom or diaphragm with contraceptive gel)

It is often taken once a day. In such cases, try to take it at the same time each day. If you are told to take it more than once each day, and if you happen to miss--or are late in taking--the medicine then take it as soon as possible. However, do not take twice the recommended dosage in order to make up for a missed dosage. Regardless of the dosage, it can be taken with, or without food (I.e., before or after a meal).

If you are taking it to treat a condition then continue to take Norethisterone even after you feel well; continue to take it until your doctor tells you to stop. Keep the medicine in a cool (77°F or 25°C) dry place, away from direct light or heat, and out of the reach and sight of children)


1) Medical conditions of you or a family member: are lactose-intolerant; allergic to Norethisterone; jaundice; rashes or itching; severe liver problems or liver tumors; kidney problems; tumors of the breast , womb or ovaries; high levels of fat in the blood; irregular or unusual vaginal bleeding of unknown cause; sickle cell anemia; the rare inherited blood condition called porphyria; heart attack, stroke or angina; a blood clot in the legs or lungs; hypertension; diabetes; depression; migraine; epilepsy; muscle spasms; gallstones; cancer; asthma; elderly; pregnant or breast-feeding; or will be bed-ridden or immobile for a period of time.

2) Medicines  Foods and even alcohol are not known to have an adverse effect on its use, but inform your doctor if you are taking and of the following: Aprepitant, Atorvastatin; Phenytoin, Primidone, Ampicillin, Rufinamide; Selegiline; medicines for cancer, medicines for blood pressure, barbiturates, corticosteroids, Rifamycin, Topiramate, Ritonavir, female sex hormones, even the medicinal herb St. John’s Wort, or any other medicine, especially anticonvulsants, anti-infectives, tetracyclines, NSAIDs or anything which cause fluid retention, cytotoxics and cytochrome P450 enzyme inducers

Other medicines presenting a concern are those that treat epilepsy (such as phenytoin and carbamazepine); antibiotics to treat an infection (such as rifampicin, co-trimoxazole and the above-mentioned tetracyclines); antiviral medicines to treat HIV (such as ritonavir and nelfinavir); anticancer medicines; medicines for suppressing the immune system (such as cyclosporin); and medicines for Cushing’s syndrome (such as aminoglutethimide).

3) Do not take it if you are a smoker. Cigarette smoking increases the risk of blood clotting, and damage to the heart and blood vessels. This is even more pronounced in heavy smoking (15 or more cigarettes each day), and in women who are 35 or more years of age.

Side Effects

As with virtually any and all medicines, there is a host of side-effects, the most commonly reported being change in menstrual flow, absence of periods, breast changes (tenderness), nausea and vomiting, change in weight, retention of fluids, rash (either with or without itching), depression, changes (usually a reduction) in libido, change in appetite and weight change, pimples and acne, excessive hair growth, hair loss, headaches, fatigue, increased sugar in the blood, bloating, a worsening of asthma, migraine, and blood pressure, and one woman reported that her ankles swelled up enormously, forcing her to not wear shoes for two weeks.

Contact your doctor if you have a feeling of pain or tightness in your chest, an unusually severe headache, jaundice, and any disturbances in your vision or hearing after taking this medicine.

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Structural Formula

norethisterone structure


norethisterone box