Norethisterone Tablets

Mechanism

Norethisterone is a synthetic form of progesterone, a female sex hormone. It stimulates progesterone function in the body as well as mimics the effects of progesterone and thickens the lining of the uterus to allow embryo implantation. In addition, it prevents abnormal uterine bleeding. The hormone also prevents the release of follicle stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland and prevents ovulation. This helps regulate the menstrual cycle and treat a range of menstrual issues.

Pharmacokinetics

• Absorption: Rapid oral absorption
• Distribution: Widely distributed, binds to plasma proteins
• Metabolism: Hepatic metabolism via reduction and conjugation
• Elimination: Renal and fecal excretion
• Half-life: ≈ 5–12 hours

Side Effects

• Nausea
• Headache
• Breast tenderness
• Weight changes
• Menstrual irregularities

Contraindication

• Pregnancy
• History of thromboembolic disorders
• Severe hepatic impairment
• Hormone-dependent cancers

Interaction

• Enzyme inducers (rifampicin, phenytoin, carbamazepine) — reduce effectiveness
• Antibiotics (tetracyclines, penicillins) — may reduce contraceptive efficacy
• Antiretrovirals (ritonavir, efavirenz) — lower plasma levels
• Other hormonal contraceptives — additive effects possible

Warning and Precautions

• Monitor liver function during therapy
• Use cautiously in patients with cardiovascular risk
• Not recommended for long-term contraception without medical supervision