An increased risk of the following serious adverse reactions has been associated with the use of oral contraceptives (see WARNINGS section):

• Thrombophlebitis
• Arterial thromboembolism
• Pulmonary embolism
• Myocardial infarction
• Cerebral hemorrhage
• Cerebral thrombosis
• Hypertension
• Gallbladder disease
• Hepatic adenomas or benign liver tumors

There is evidence of an association between the following conditions and the use of oral contraceptives, although additional confirmatory studies are needed:

• Mesenteric thrombosis
• Retinal thrombosis

The following adverse reactions have been reported in patients receiving oral contraceptives and are believed to be drug-related:

• Nausea
• Vomiting
• Gastrointestinal symptoms (such as abdominal cramps and bloating)
• Breakthrough bleeding
• Spotting
• Change in menstrual flow
• Amenorrhea
• Temporary infertility after discontinuation of treatment
• Edema
• Melasma which may persist
• Breast changes: tenderness, enlargement, secretion
• Change in weight (increase or decrease)
• Change in cervical erosion and secretion
• Diminution in lactation when given immediately postpartum
• Cholestatic jaundice
• Migraine
• Rash (allergic)
• Mental depression
• Reduced tolerance to carbohydrates
• Vaginal candidiasis
• Change in corneal curvature (steepening)
• Intolerance to contact lenses

The following adverse reactions have been reported in users of oral contraceptives and the association has been neither confirmed nor refuted:

• Pre-menstrual syndrome
• Cataracts
• Changes in appetite
• Cystitis-like syndrome
• Headache
• Nervousness
• Dizziness
• Hirsutism
• Loss of scalp hair
• Erythema multiforme
• Erythema nodosum
• Hemorrhagic eruption
• Vaginitis
• Porphyria
• Impaired renal function
• Hemolytic uremic syndrome
• Budd-Chiari syndrome
• Acne
• Changes in libido
• Colitis

Read the Estrostep Fe (norethindrone acetate and ethinyl estradiol tablets) Side Effects Center for a complete guide to possible side effects »

Effects of Other Drugs on Oral Contraceptives

Rifampin: Metabolism of both norethindrone and ethinyl estradiol is increased by rifampin. A reduction in contraceptive effectiveness and increased incidence of breakthrough bleeding and menstrual irregularities have been associated with concomitant use of rifampin.

Anticonvulsants: Anticonvulsants such as phenobarbital, phenytoin, and carbamazepine, have been shown to increase the metabolism of ethinyl estradiol and/or norethindrone, which could result in a reduction in contraceptive effectiveness.

Antibiotics: Pregnancy while taking oral contraceptives has been reported when the oral contraceptives were administered with antimicrobials such as ampicillin, tetracycline, and griseofulvin. However, clinical pharmacokinetic studies have not demonstrated any consistent effect of antibiotics (other than rifampin) on plasma concentrations of synthetic steroids.

Atorvastatin: Coadministration of atorvastatin and an oral contraceptive increased AUC values for norethindrone and ethinyl estradiol by approximately 30% and 20%, respectively.

St. John's Wort: Herbal products containing St. John's Wort (hypericum perforatum) may induce hepatic enzymes (cytochrome P450) and p-glycoprotein transporter and may reduce the effectiveness of oral contraceptives. This may also result in breakthrough bleeding.

Other: Ascorbic acid and acetaminophen may increase plasma ethinyl estradiol concentrations, possibly by inhibition of conjugation. A reduction in contraceptive effectiveness and increased incidence of breakthrough bleeding has been suggested with phenylbutazone.

Effects of Oral Contraceptives on Other Drugs

Oral contraceptive combinations containing ethinyl estradiol may inhibit the metabolism of other compounds. Increased plasma concentrations of cyclosporine, prednisolone, and theophylline have been reported with concomitant administration of oral contraceptives. In addition, oral contraceptives may induce the conjugation of other compounds. Decreased plasma concentrations of acetaminophen and increased clearance of temazepam, salicylic acid, morphine, and clofibric acid have been noted when these drugs were administered with oral contraceptives.

Interactions with Laboratory Tests

Certain endocrine and liver function tests and blood components may be affected by oral contraceptives:

1. Increased prothrombin and factors VII, VIII, IX, and X; decreased antithrombin 3; increased norepinephrine-induced platelet aggregability.
2. Increased thyroid binding globulin (TBG) leading to increased circulating total thyroid hormone, as measured by protein-bound iodine (PBI), T₄ by column or by radioimmunoassay. Free T₃ resin uptake is decreased, reflecting the elevated TBG; free T₄ concentration is unaltered.
3. Other binding proteins may be elevated in serum.
4. Sex-binding globulins are increased and result in elevated levels of total circulating sex steroids and corticoids; however, free or biologically active levels remain unchanged.
5. Triglycerides may be increased.
6. Glucose tolerance may be decreased.
7. Serum folate levels may be depressed by oral contraceptive therapy. This may be of clinical significance if a woman becomes pregnant shortly after discontinuing oral contraceptives.

Last reviewed on RxList: 4/28/2008
This monograph has been modified to include the generic and brand name in many instances.