Norethisterone

Indications

Norethisterone is used for: Breast cancer, Metropathia haemorrhagica (dysfunctional uterine bleeding), Premenstrual syndrome, Contraception, Endometriosis, Menorrhagia, Menopausal HRT

Adult Dose

Oral Adult Abnormal bleeding – 1 tablet three times a day for 10 days. Bleeding usually stops within 1-3 days. A period usually starts 2-4 days after stopping treatment. Prevention of abnormal bleeding – 1 tablet twice a day from the 19th - 26th day of the cycle. Premenstrual Syndrome - 2 to 3 tablets a day from the 19th - 26th day of the cycle. You will normally be treated for several months. Delaying a period - 1 tablet three times a day starting three days before the expected beginning of the period. Your period should occur 2-3 days after you have stopped taking the medicine. Dysmenorrhea (Painful periods) - 1 tablet three times a day for 20 days starting on the 5th day of the cycle. You will usually be treated for 3-4 cycles. Menorrhagia (Heavy periods) - 1 tablet two to three times a day from the 19th - 26th day of the cycle. Endometriosis - 2 tablets a day starting on the 5th day of your cycle. If you continue having small bleeds (“spotting”), the dosage may be increased to 4 to 5 tablets a day. Once bleeding has stopped the dosage may be reduced. You will usually be treated continuously for 4-6 months or longer. (Counting the first day of menstruation as day 1).

Child Dose

Renal Dose

Administration

May be taken with or without food.

Contra Indications

Severe hepatic dysfunction; undiagnosed vaginal bleeding; porphyria; pregnancy; previous idiopathic or current thromboembolism; thromboembolic disease; DVT.

Precautions

Hypertension; CVS disease; hepatic impairment; epilepsy; lactation; new onset of migraine-type headache; asthma; renal impairment; history of clinical depression.

Pregnancy-Lactation

Interactions

Concentration may be reduced by CYP450 inducers (e.g. phenobarbital, phenytoin, carbamazepine, rifampicin, rifabutin, nevirapine, efavirenz, tetracyclines, ampicillin, oxacillin, co-trimoxazole) and ritonavir, nelfinavir (usually inhibitors of CYP450 but have inducing properties when used with steroid hormones). May cause additive fluid retention with NSAIDs, vasodilators. Adjustment in antidiabetic, thyroid hormone and anticoagulant therapy may be required. Potentially Fatal: May increase ciclosporin concentration.

Adverse Effects

Side effects of Norethisterone : Mental depression, cholestatic jaundice, porphyria, epilepsy, migraine, headache, breast discomfort, dizziness, nausea and vomiting, changes in libido, appetite and weight, breakthrough bleeding, changes in menstrual flow, amenorrhoea, oedema, rash, melasma or cholasma, acne, urticaria, abnormal LFTs, moodswings, insomnia, thrombotic and thromoembolic events, optic neuritis, altered lipid profile.

Mechanism of Action

Norethisterone has typical effects of a progestogen and converts the endometrium from the proliferative to the secretory phase. It may also have some oestrogenic, anabolic and androgenic activities, but these may not be significant. Norethisterone delays onset of periods and controls abnormal uterine bleeding. It also has contraceptive effects due to negative feedback inhibition of pituitary gonadotropin thus preventing ovulation.