"What are birth control pills and how do they work?
Birth control pills are also known as oral contraceptives (OCs) or, simply, “the pill.” They offer protection against pregnancy by blocking the union of sperm and egg, thereby prevent"...
An increased risk of the following serious adverse reactions (see "WARNINGS" section for additional information) has been associated with the use of oral contraceptives.
Thromboembolic disorders and other vascular problems (including thrombophlebitis, arterial thromboembolism, pulmonary embolism, myocardial infarction, cerebral hemorrhage, cerebral thrombosis), carcinoma of the reproductive organs, hepatic neoplasia (including hepatic adenomas or benign liver tumors), ocular lesions (including retinal vascular thrombosis), gallbladder disease, carbohydrate and lipid effects, elevated blood pressure, and headache.
The following adverse reactions have been reported in patients receiving oral contraceptives and are believed to be drug related:
Gastrointestinal symptoms (such as abdominal pain, cramps and bloating).
Change in menstrual flow.
Temporary infertility after discontinuation of treatment.
Melasma/chloasma which may persist.
Breast changes: tenderness, pain, enlargement, secretion.
Change in weight or appetite (increase or decrease).
Change in cervical erosion and secretion.
Diminution in lactation when given immediately postpartum.
Mood changes, including depression.
Vaginitis, including candidiasis.
Change in corneal curvature (steepening).
Intolerance to contact lenses.
Decrease in serum folate levels.
Exacerbation of systemic lupus erythematosus.
Exacerbation of porphyria.
Exacerbation of chorea.
Aggravation of varicose veins.
Anaphylactic/anaphylactoid reactions, including urticaria, angioedema, and severe reactions with respiratory and circulatory symptoms.
The following adverse reactions have been reported in users of oral contraceptives, and the association has been neither confirmed nor refuted:
Optic neuritis, which may lead to partial or complete loss of vision.
Loss of scalp hair.
Impaired renal function.
Hemolytic uremic syndrome.
Changes in libido.
Cerebral-vascular disease with mitral valve prolapse.
Read the Trivora-28 (levonorgestrel and ethinyl estradiol) Side Effects Center for a complete guide to possible side effects
Interactions between ethinyl estradiol and other substances may lead to decreased or increased serum ethinyl estradiol concentrations.
Decreased ethinyl estradiol plasma concentrations may cause an increased incidence of breakthrough bleeding and menstrual irregularities and may possibly reduce efficacy of the combination oral contraceptive.
Reduced ethinyl estradiol concentrations have been associated with concomitant use of substances that induce hepatic microsomal enzymes, such as rifampin, rifabutin, barbiturates, phenylbutazone, phenytoin sodium, griseofulvin, topiramate, some protease inhibitors, modafinil, and possibly St. John's wort.
Substances that may decrease plasma ethinyl estradiol concentrations by other mechanisms include any substance that reduces gut transit time and certain antibiotics (e.g. ampicillin and other penicillins, tetracyclines) by a decrease of enterohepatic circulation of estrogens. During concomitant use of ethinyl estradiol containing products and substances that may lead to decreased plasma steroid hormone concentrations, it is recommended that a nonhormonal back-up method of birth control be used in addition to the regular intake of Trivora (levonorgestrel and ethinyl estradiol tablets-triphasic regimen). If the use of a substance which leads to decreased ethinyl estradiol plasma concentrations is required for a prolonged period of time, combination oral contraceptives should not be considered the primary contraceptive.
After discontinuation of substances that may lead to deceased ethinyl estradiol plasma concentrations, use of a nonhormonal back-up method of birth control is recommended for 7 days. Longer use of a back-up method is advisable after discontinuation of substances that have led to induction of hepatic microsomal enzymes, resulting in decreased ethinyl estradiol concentrations. It may take several weeks until enzyme induction has completely subsided, depending on dosage, duration of use, and rate of elimination of the inducing substance.
Some substances may increase plasma ethinyl estradiol concentrations. These include:
- Competitive inhibitors for sulfation of ethinyl estradiol in the gastrointestinal wall, such as ascorbic acid (vitamin C) and acetaminophen.
- Substances that inhibit cytochrome P450 3A4 isoenzymes such as indinavir, fluconazole, and troleandomycin. Troleandomycin may increase the risk of intrahepatic cholestasis during coadministration with combination oral contraceptives.
- Atorvastatin (unknown mechanism).
Ethinyl estradiol may interfere with the mechanism of other drugs by inhibiting hepatic microsomal enzymes or by inducing hepatic drug conjugation, particularly glucuronidation. Accordingly, tissue concentrations may be either increased (e.g. cyclosporine, theophylline, corticosteroids) or decreased.
The prescribing information of concomitant medications should be consulted to identify potential interactions.
Interactions With Laboratory Tests
Certain endocrine- and liver-function tests and blood components may be affected by oral contraceptives:
- Increased prothrombin and factors VII, VIII, IX, and X; decreased antithrombin 3; increased norepinephrine-induced platelet aggregability.
- 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.
- Other binding proteins may be elevated in serum.
- 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.
- Triglycerides may be increased.
- Glucose tolerance may be decreased.
- 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.
Read the Trivora-28 Drug Interactions Center for a complete guide to possible interactions
Last reviewed on RxList: 3/26/2008
Additional Trivora-28 Information
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