home > drugs a-z list > femhrt (norethindrone acetate, ethinyl estradiol) drug center > femhrt (norethindrone acetate, ethinyl estradiol) drug - side effects and drug interactions

See BOXED WARNING, WARNINGS and PRECAUTIONS.

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The adverse reaction information from clinical trials does, however, provide a basis for identifying the adverse events that appear to be related to drug use and for approximating rates.

Adverse events reported in controlled clinical studies of femhrt (norethindrone acetate, ethinyl estradiol) are shown in Table 6 below.

Table 6. All Treatment-Emergent Adverse Events Reported at a Frequency of ≥ 5% of Patients with femhrt (norethindrone acetate, ethinyl estradiol)

The following additional adverse reactions have been reported with estrogen and/or progestin therapy.

Genitourinary system

Changes in vaginal bleeding pattern and abnormal withdrawal bleeding or flow; breakthrough bleeding; spotting; increase in size of uterine leiomyomata, vaginitis, including vaginal candidiasis; change in amount of cervical secretion; changes in cervical ectropion; ovarian cancer; endometrial hyperplasia; endometrial cancer.

Breasts

Tenderness, enlargement, pain, nipple discharge, galactorrhea; fibrocystic breast changes; breast cancer.

Cardiovascular

Deep and superficial venous thrombosis; pulmonary embolism; thrombophlebitis; myocardial infarction; stroke; increase in blood pressure.

Gastrointestinal

Nausea, vomiting; cholestatic jaundice; pancreatitis, enlargement of hepatic hemangiomas; bloating, abdominal cramps; increased incidence of gallbladder disease.

Skin

Chloasma or melasma that may persist when drug is discontinued; erythema multiforme; erythema nodosum; hemorrhagic eruption; loss of scalp hair; hirsutism; rash, pruritus.

Eyes

Retinal vascular thrombosis, intolerance to contact lenses.

Central nervous system

Headache; migraine; dizziness; mental depression; chorea; nervousness; mood disturbances; irritability; exacerbation of epilepsy, dementia.

Miscellaneous

Increase or decrease in weight; reduced carbohydrate tolerance; aggravation of porphyria; edema; arthalgias; leg cramps; changes in libido; urticaria, angioedema, anaphylactoid/anaplylactic reactions; hypocalcemia; exacerbation of asthma; increased triglycerides.

Drug/Laboratory Test Interactions

The following drug/laboratory interactions have been observed with estrogen therapy, and/or femhrt (norethindrone acetate, ethinyl estradiol) :

1. In a 12-week study, femhrt (norethindrone acetate, ethinyl estradiol) 0.5/2.5 and femhrt (norethindrone acetate, ethinyl estradiol) 1/5 decreased Factor VII, and femhrt (norethindrone acetate, ethinyl estradiol) 1/5 decreased plasminogen activator inhibitor-1 from baseline in a dose-related manner but remained within the laboratory reference range for postmenopausal women. Mean levels of fibrinogen and partial thromboplastin time changed minimally from baseline for femhrt (norethindrone acetate, ethinyl estradiol) 0.5/2.5 and femhrt (norethindrone acetate, ethinyl estradiol) 1/5.
2. Estrogen therapy may increase thyroxine-binding globulin (TBG), leading to increased circulating total thyroid hormone (T₄) as measured by protein-bound iodine (PBI), T₄ levels (by column or radioimmunoassay), or T₃ levels by radioimmunoassay. T₃ resin uptake is decreased, reflecting the elevated TBG. Free T₄ and free T₃ concentrations are unaltered. Patients on thyroid replacement therapy may require higher doses of thyroid hormone.
3. Estrogen therapy may elevate other binding proteins in serum, i.e., corticosteroid binding globulin (CBG), sex hormone binding globulin (SHBG), leading to increased circulating corticosteroids and sex steroids, respectively. Free hormone concentrations may be decreased. Other plasma proteins may be increased (angiotensinogen/renin substrate, alpha-1-antitrypsin, ceruloplasmin). femhrt (norethindrone acetate, ethinyl estradiol) 0.5/2.5 and femhrt (norethindrone acetate, ethinyl estradiol) 1/5 were associated with an SHBG increase of 15% and 22%, respectively.
4. Estrogen therapy increases plasma HDL and HDL₂ subfraction concentrations, reduces LDL cholesterol concentration and increases triglyceride levels.
5. Estrogen therapy is associated with impaired glucose tolerance.
6. Estrogen therapy reduces response to metyrapone test.

Drug/Drug Interactions

No drug-drug interaction studies have been conducted with femhrt (norethindrone acetate, ethinyl estradiol) .

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 preparations (Hypericum perforatum), Phenobarbital, carbamazepine, and rifampin may reduce plasma concentrations 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, intraconazole, ritonavir and grapefruit juice may increase plasma concentrations of estrogens and may result in side effects.

The following section contains information on drug interactions with ethinyl estradiol-containing products (specifically, oral contraceptives) that have been reported in the public literature. It is unknown whether such interactions occur with femhrt (norethindrone acetate, ethinyl estradiol) or drug products containing other types of estrogens.

The Effect of Ethinyl Estradiol on Other Drugs

Drug products containing ethinyl estradiol may inhibit the metabolism of other compounds. Increased plasma concentrations of cyclosporin, prednisolone, and theophylline have been reported with concomitant administration of certain drugs containing ethinyl estradiol (e.g., oral contraceptives containing ethinyl estradiol). In addition, drugs containing ethinyl estradiol may induce the conjugation of other compounds.

Decreased plasma concentrations of acetaminophen and increased clearance of temazapam, salicylic acid, morphine, and clofibric acid have been noted when these drugs were administered with certain ethinyl-estradiol containing drug products (e.g., oral contraceptives containing ethinyl estradiol).

Last reviewed on RxList: 1/23/2009
This monograph has been modified to include the generic and brand name in many instances.