Norethisteron Zentiva (Norethisterone Acetate)

Norethisteron Zentiva, a progestogen, is indicated for conditions that involve hormonal regulation of the menstrual cycle.

• Contraception: prevents pregnancy by suppressing ovulation and inducing endometrial changes that inhibit implantation.
• Menstrual disorders: reduces heavy menstrual bleeding and stabilises irregular cycles.
• Endometriosis: alleviates pain associated with endometrial tissue growth outside the uterus.

• Norethisterone acetate is a synthetic progestogen that binds with high affinity to progesterone receptors in the hypothalamic‑pituitary‑ovarian axis. Receptor activation suppresses the luteinising hormone surge, thereby inhibiting ovulation, and induces secretory transformation of the endometrium, creating an environment unsuitable for implantation.

Oral administration of norethisterone acetate may be associated with a range of adverse reactions.

Common Side Effects

• Nausea
• Breast tenderness
• Headache
• Weight gain or loss
• Mood changes
• Spotting or breakthrough bleeding

Serious or Rare Side Effects

• Deep vein thrombosis or pulmonary embolism
• Severe allergic reaction (anaphylaxis)
• Liver dysfunction or jaundice
• Unexplained vaginal bleeding
• High blood pressure
• Visual disturbances

Before prescribing Norethisteron Zentiva, clinicians should evaluate the following safety considerations.

• Assess medical history: identify risk factors for thromboembolism, cardiovascular disease, or liver disorders.
• Avoid use in pregnancy: contraindicated for women who are or may become pregnant.
• Review concomitant medications: consider interactions that may reduce contraceptive efficacy.
• Monitor for mood or metabolic changes: observe for depression, weight fluctuations, or glucose intolerance.
• Counsel on bleeding patterns: inform patients about possible spotting or breakthrough bleeding.
• Store at ambient temperature: keep tablets in the original container, protect from moisture and light.

Norethisterone acetate can affect, or be affected by, other medicines. Interactions are grouped by clinical significance.

Major Interactions (Avoid)

• Strong CYP3A4 inducers (e.g., rifampicin, carbamazepine, phenytoin): may markedly reduce contraceptive effectiveness.
• Potent CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): can increase progestogen levels and risk of side effects.
• Certain HIV protease inhibitors (e.g., ritonavir): may alter hormone metabolism leading to unpredictable efficacy.

Moderate Interactions (Monitor Closely)

• Moderate enzyme‑inducing anticonvulsants (e.g., phenobarbital, topiramate): may modestly lower drug levels.
• St. John’s wort: may decrease hormonal activity, requiring additional contraceptive measures.
• Tetracycline antibiotics: generally have minimal effect but monitoring is advised.