Norethisterone Acetate

Indications

Norethisterone is indicated in:
  • Metropathia hemorrhagic (dysfunctional uterine bleeding),
  • Premenstrual syndrome,
  • Postponement of menstruation,
  • Endometriosis &
  • Menorrhagia.

Therapeutic Class

Drugs for menopausal symptoms: Hormone replacement therapy, Female Sex hormones, Oral Contraceptive preparations

Pharmacology

Norethisterone tablet is a preparation of Norethisterone which has progestational actions similar to those of progesterone, but is a more potent inhibitor of ovulation and has weak estrogenic and androgenic properties. It is used to treat a number of disorders of the menstrual cycle. Norethisterone is absorbed from the gastrointestinal tract and its effects last for at least 24 hours. It is excreted in the urine.

Dosage & Administration

Oral administration. Not intended for use in children.

Metropathia haemorrhagica (dysfunctional uterine bleeding): 1 tablet 3 times daily for 10 days. Bleeding is arrested usually within 1-3 days. A withdrawal bleeding resembling normal menstruation occurs within 2-4 days after discontinuing treatment.

Prophylaxis against recurrence of dysfunctional bleeding: If there are no signs of resumption of normal ovarian function (no rise in the second half of the cycle of the morning temperature, which should be measured daily) recurrence must be anticipated. Cyclical bleeding can be established with 1 tablet twice daily from the 19th to the 26th day of the cycle.

Premenstrual syndrome (including premenstrual mastalgia): Premenstrual symptoms such as headache, migraine, breast discomfort, water retention, tachycardia, and psychological disturbances may be relieved by the administration of 2-3 tablets daily from the 19th to the 26th day of the cycle. Treatment should be repeated for several cycles. When treatment is stopped, the patient may remain symptom-free for a number of months.

Postponement of menstruation: In cases of too frequent menstrual bleeding, and in special circumstances (e.g. operations, travel, sports) the postponement of menstruation is possible. 1 tablet of Norethisterone three times daily, starting 3 days before the expected onset of menstruation. A normal period should occur 2-3 days after the patient has stopped taking tablets.

Endometriosis (pseudo-pregnancy therapy): Long-term treatment is commenced on the 5th day of the cycle with 2 tablets of Norethisterone daily for the first few weeks. In the event of spotting, the dosage is increased to 4, and, if necessary, 5 tablets daily. After bleeding has ceased, the initial dose is usually sufficient. Duration of treatment: 4-6 months continuously, or longer if necessary.

Menorrhagia (hypermenorrhoea): 1 tablet 2-3 times a day from the 19th to the 26th day of the cycle (counting the first day of menstruation as day 1).

Interaction

Not known.

Contraindications

  • Pregnancy
  • Severe disturbances of liver function
  • Dubin-Johnson syndrome
  • Rotor syndrome
  • Previous or existing liver tumours
  • History during pregnancy of idiopathic jaundice, severe pruritus or herpes gestationis
  • Current thromboembolic processes
  • Hypersensitivity to the active substances or to any of the excipients

Side Effects

Side-effects are more common during the first months after start of intake of Norethisterone, and subside with a duration of treatment. The side-effects are mentioned below:
  • Eye disorders- Visual disturbance
  • GI disorders- Nausea
  • General disorders and administration site- conditions headache, edema
  • Nervous system disorders- Migraine, Respiratory, thoracic and mediastinal disorders- Dyspnoea,
  • Skin and subcutaneous tissue disorders- Hypersensitivity (eg. Rash, urticaria).

Pregnancy & Lactation

The administration of Norethisterone during pregnancy is contraindicated. Norethisterone should not be used during lactation.

Precautions & Warnings

There is a general opinion, based on statistical evidence that users of combined oral contraceptives experience, more often than non-users, venous thromboembolism, arterial thrombosis, including cerebral and myocardial infarction and subarachnoid haemorrhage. Full recovery from such disorders does not always occur, and it should be realized that in a few cases they are fatal. Although Norethisterone does not contain oestrogen, one should keep the possibility of an increased thromboembolic risk in mind, particularly where there is a history of thromboembolic disease or in the presence of severe diabetes with vascular changes or sickle-cell anaemia.

In rare cases benign, and in even rarer cases, malignant liver tumours leading in isolated cases to life-threatening intra-abdominal haemorrhage have been observed after the use of hormonal substances such as the one contained in Norethisterone. If severe upper abdominal complaints, liver enlargement or signs of intra-abdominal haemorrhage occur, a liver tumour should be included in the differential diagnosis and, if necessary, the preparation should be withdrawn.
Norethisterone can influence carbohydrate metabolism. Parameters of carbohydrate metabolism should be examined carefully in all diabetics before and regularly during treatment.

Reasons for stopping Norethisterone immediately-
  • Occurrence for the first time of migrainous headaches or more frequent occurrence of unusually severe headaches
  • Sudden perceptual disorders (e.g. disturbances of vision or hearing)
  • First signs of thrombophlebitis or thromboembolic symptoms, feeling of pain and tightness in the chest
  • Pending operations (six weeks beforehand), immobilisation (e.g. after accidents)
  • Onset of jaundice, hepatitis, general pruritus
  • Significant rise in blood pressure
  • Pregnancy.

Overdose Effects

There have been no reports from overdosage and treatment is generally unnecessary. There are no special antidotes and treatment should be symptomatic.

Storage Conditions

Store below 30°C in a cool & dry place. Keep out of reach of children.