Norethindrone Acetate

Pronunciation

Pronunciation: nor-eth-IN-drone ASS-uh-TATE
Class: Progestin

Trade Names

Aygestin
- Tablets 5 mg

Micronor (Canada)

Pharmacology

Inhibits secretion of pituitary gonadotropins, thereby preventing follicular maturation and ovulation.

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Pharmacokinetics

Absorption

Norethindrone acetate is rapidly absorbed from GI tract. T max is approximately 2 h.

Distribution

Rapid distribution of dorethindrone acetate.

Metabolism

Norethindrone is metabolized in the liver.

Elimination

Norethindrone elimination is rapid, primarily in feces.

Indications and Usage

Treatment of secondary amenorrhea; endometriosis; abnormal uterine bleeding caused by hormonal imbalance in the absence of organic pathology (eg, uterine cancer).

Contraindications

Thrombophlebitis, thrombolic disorders, cerebral apoplexy, or a history of these conditions; markedly impaired liver function or liver disease; known or suspected carcinoma of the breast; undiagnosed vaginal bleeding; missed abortion; as a diagnostic test for pregnancy.

Dosage and Administration

Secondary Amenorrhea, Abnormal Uterine Bleeding
Adults

PO 2.5 to 10 mg/day for 5 to 10 days during second half of the theoretical menstrual cycle.

Endometriosis
Adults

PO 5 mg/day initially for 2 wk, then increase in increments of 2.5 mg/day every 2 wk until 15 mg/day is achieved. Therapy may be continued at this level for 6 to 9 mo or until breakthrough bleeding demands temporary termination.

General Advice

  • Administer once daily, without regard to meals. Administer with food if GI upset occurs.

Storage/Stability

Store at controlled room temperature (59° to 86°F).

Drug Interactions

Rifampin

Elimination of norethindrone may be increased, decreasing the therapeutic effect.

Laboratory Test Interactions

Pregnanediol determinations may be altered; thyroid and LFT results may be affected; increased amounts of coagulation factors; reduced response to metyrapone test.

Adverse Reactions

Cardiovascular

Thrombophlebitis; cerebral thrombosis and embolism; hypertension; edema.

CNS

Depression; changes in libido; changes in appetite; headache; nervousness; dizziness; fatigue.

Dermatologic

Allergic rash; melasma; chloasma; hirsutism; alopecia; erythema multiforme; erythema nodosum; hemorrhagic eruption; itching.

EENT

Neuro-ocular lesions (eg, retinal thrombosis, optic neuritis).

Genitourinary

Breakthrough bleeding; spotting; amenorrhea; increased cervical erosion and secretion; cystitis.

Hepatic

Cholestatic jaundice.

Metabolic

Weight gain and loss.

Respiratory

Pulmonary embolism.

Miscellaneous

Premenstrual syndrome; backache.

Precautions

Pregnancy

Category X .

Lactation

Excreted in breast milk.

Children

Safety and efficacy not established.

Fluid retention

Use with careful observation when conditions that might be affected by fluid retention are present (eg, asthma, cardiac or renal dysfunction, epilepsy).

Mental depression

Carefully observe patients with history of depression.

Ophthalmic effects

Discontinue therapy if there are any sudden changes in vision or onset of proptosis, diplopia, migraine, papilledema, or retinal vascular lesions.

Patient Information

  • Instruct patient to take once daily as prescribed.
  • Advise patient that medication can be taken without regard to meals, but to take with food if GI upset occurs.
  • Warn women of childbearing potential of significant risks associated with taking this medication and becoming pregnant.
  • Instruct diabetic patient to monitor blood glucose more frequently when drug is started or dose is changed and to inform health care provider of significant changes in readings.
  • Instruct patient to report the following symptoms to health care provider: pain in groin or calves; sharp chest pain or sudden shortness of breath; abnormal vaginal bleeding; sudden severe headache or migraine headache; vision problems; yellowing of skin or eyes; or depression.

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