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Femhrt (Norethindrone Acetate / Ethinyl Estradiol) - Drug Interactions, Contraindications, Overdosage, etc

 
 



DRUG INTERACTIONS

No drug-drug interaction studies have been conducted for femhrt.

Effect of Other Drugs on Combined Hormonal Products

Substances decreasing or increasing the plasma concentration of estrogen: In vitro and in vivo studies have shown that estrogens are metabolized partially by cytochrome P450 3A4 (CYP3A4). Therefore, inducers or inhibitors of CYP3A4 may affect estrogen drug metabolism. Inducers of CYP3A4 such as St. John’s wort (Hypericum perforatum) preparations, phenobarbital, carbamazepine and rifampin may decrease the plasma concentration of estrogens, possibly resulting in a decrease in therapeutic effects and/or changes in the uterine bleeding profile. Inhibitors of CYP3A4 such as erythromycin, clarithromycin, ketoconazole, itraconazole, ritonavir and grapefruit juice may increase the plasma concentration of estrogens and may result in side effects. Co-administration of atorvastatin and certain hormonal products containing ethinyl estradiol increase AUC values for ethinyl estradiol approximately 20 percent. Ascorbic acid and acetaminophen may increase the plasma ethinyl estradiol concentration, possibly by inhibition of conjugation.

Effect of Combined Hormonal Products on Other Drugs

Combination hormonal products containing some synthetic estrogens (for example, ethinyl estradiol) may inhibit the metabolism of other compounds. Combination hormonal products have been shown to significantly decrease the plasma concentration of lamotrigine likely due to induction of lamotrigine glucuronidation. This may reduce seizure control; therefore, dosage adjustments of lamotrigine may be necessary.

OVERDOSAGE

Overdosage of estrogen plus progestin may cause nausea, vomiting, breast tenderness, abdominal pain, drowsiness and fatigue, and withdrawal bleeding may occur in women. Treatment of overdose consists of discontinuation of femhrt with institution of appropriate symptomatic care.

CONTRAINDICATIONS

femhrt is contraindicated in women with any of the following conditions:

  • Undiagnosed abnormal genital bleeding
  • Known, suspected, or history of breast cancer
  • Known or suspected estrogen-dependent neoplasia
  • Active DVT, PE or a history of these conditions
  • Active arterial thromboembolic disease (for example, stroke and MI), or a history of these conditions
  • Known anaphylactic reaction or angioedema to femhrt
  • Known liver impairment or disease
  • Known protein C, protein S, or antithrombin deficiency, or other known thrombophilic disorders
  • Known or suspected pregnancy

REFERENCES

  1. Rossouw JE, et al. Postmenopausal Hormone Therapy and Risk of Cardiovascular Disease by Age and Years Since Menopause. JAMA. 2007;297:1465-1477.
  2. Hsia J, et al. Conjugated Equine Estrogens and Coronary Heart Disease. Arch Int Med. 2006;166:357-365.
  3. Cushman M, et al. Estrogen Plus Progestin and Risk of Venous Thrombosis. JAMA. 2004;292:1573-1580.
  4. Curb JD, et al. Venous Thrombosis and Conjugated Equine Estrogen in Women Without a Uterus. Arch Int Med. 2006;166:772-780.
  5. Chlebowski RT, et al. Influence of Estrogen Plus Progestin on Breast Cancer and Mammography in Healthy Postmenopausal Women. JAMA. 2003;289:3234-3253.
  6. Stefanick ML, et al. Effects of Conjugated Equine Estrogens on Breast Cancer and Mammography Screening in Postmenopausal Women With Hysterectomy. JAMA. 2006;295:1647-1657.
  7. Anderson GL, et al. Effects of Estrogen Plus Progestin on Gynecologic Cancers and Associated Diagnostic Procedures. JAMA. 2003;290:1739-1748.
  8. Shumaker SA, et al. Conjugated Equine Estrogens and Incidence of Probable Dementia and Mild Cognitive Impairment in Postmenopausal Women. JAMA. 2004;291:2947-2958.
  9. Jackson RD, et al. Effects of Conjugated Equine Estrogen on Risk of Fractures and BMD in Postmenopausal Women With Hysterectomy: Results From the Women’s Health Initiative Randomized Trial. J Bone Miner Res. 2006;21:817-828.
  10. Hendrix SL, et al. Effects of Conjugated Equine Estrogen on Stroke in the Women’s Health Initiative. Circulation. 2006;113:2425-2434.

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