"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 and thrombotic disorders and other vascular problems (including thrombophlebitis and venous thrombosis with or without pulmonary embolism, mesenteric thrombosis, arterial thromboembolism, myocardial infarction, cerebral hemorrhage, cerebral thrombosis, transient ischemic attack), carcinoma of the reproductive organs and breasts, hepatic neoplasia/liver disease (including hepatic adenomas or benign liver tumors), ocular lesions (including retinal vascular thrombosis), gallbladder disease, carbohydrate and lipid effects, elevated blood pressure, and headache including migraine.
The following adverse reactions have been reported in patients receiving oral contraceptives and are believed to be drug related (alphabetically listed):
Anaphylactic/anaphylactoid reactions, including urticaria, angioedema, and severe reactions with respiratory and circulatory symptoms
Breast changes: tenderness, pain, enlargement, secretion
Cervical erosion and secretion, change in
Chorea, exacerbation of
Contact lenses, intolerance to
Corneal curvature (steepening), change in
Focal nodular hyperplasia
Gastrointestinal symptoms (such as abdominal pain, cramps, and bloating)
Infertility after discontinuation of treatment, temporary
Lactation, diminution in, when given immediately postpartum
Libido, change in
Melasma/chloasma which may persist
Menstrual flow, change in
Mood changes, including depression
Porphyria, exacerbation of
Scalp hair, loss of
Serum folate levels, decrease in
Systemic lupus erythematosus, exacerbation of
Vaginitis, including candidiasis
Varicose veins, aggravation of
Weight or appetite (increase or decrease), change in
The following adverse reactions have been reported in users of oral contraceptives
Hemolytic uremic syndrome
Optic neuritis, which may lead to partial or complete loss of vision
Renal function, impaired
Read the Lybrel (levonorgestrel and ethinyl estradol tablets) Side Effects Center for a complete guide to possible side effects »
Changes in Contraceptive Effectiveness Associated with Coadministration of Other Products: Contraceptive effectiveness may be reduced when hormonal contraceptives are coadministered with antibiotics, anticonvulsants, and other drugs that increase the metabolism of contraceptive steroids. This could result in unintended pregnancy or unscheduled bleeding. Examples include rifampin, rifabutin, barbiturates, primidone, phenylbutazone, phenytoin, dexamethasone, carbamazepine, felbamate, oxcarbazepine, topiramate, griseofulvin, and modafinil. In such cases a nonhormonal back-up method of birth control should be considered.
Several cases of contraceptive failure and unscheduled bleeding have been reported in the literature with concomitant administration of antibiotics such as ampicillin and other penicillins, and tetracyclines. However, clinical pharmacology studies investigating drug interactions between combined oral contraceptives and these antibiotics have reported inconsistent results. Enterohepatic recirculation of estrogens may also be decreased by substances that reduce gut transit time.
Several of the anti-HIV protease inhibitors have been studied with coadministration of oral combination hormonal contraceptives; significant changes (increase and decrease) in the plasma levels of the estrogen and progestin have been noted in some cases. The safety and efficacy of oral contraceptive products may be affected with coadministration of anti-HIV protease inhibitors. Health care professionals should refer to the label of the individual anti-HIV protease inhibitors for further drug-drug interaction information.
Herbal products containing St. John's Wort (Hypericum perforatum) may induce hepatic enzymes (cytochrome P 450) and p-glycoprotein transporter and may reduce the effectiveness of contraceptive steroids. This may also result in unscheduled bleeding.
Increase in Plasma Levels Associated with Coadministered Drugs
Coadministration of atorvastatin and certain oral contraceptives containing ethinyl estradiol increases AUC values for ethinyl estradiol by approximately 20%. Ascorbic acid and acetaminophen increase the bioavailability of ethinyl estradiol since these drugs act as competitive inhibitors for sulfation of ethinyl estradiol in the gastrointestinal wall, a known pathway of elimination for ethinyl estradiol. CYP 3A4 inhibitors such as indinavir, itraconazole, ketoconazole, fluconazole, and troleandomycin may increase plasma hormone levels. Troleandomycin may also increase the risk of intrahepatic cholestasis during coadministration with combination oral contraceptives.
Changes in Plasma Levels of Coadministered Drugs
Combination hormonal contraceptives containing some synthetic estrogens (eg, ethinyl estradiol) may inhibit the metabolism of other compounds. Increased plasma concentrations of cyclosporine, prednisolone and other corticosteroids, and theophylline have been reported with concomitant administration of oral contraceptives. Decreased plasma concentrations of acetaminophen and lamotrigine, and increased clearance of temazepam, salicylic acid, morphine, and clofibric acid, due to induction of conjugation (particularly glucuronidation), have been noted when these drugs were administered with oral contraceptives.
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 ie, corticosteroid binding globulin (CBG), sex hormone-binding globulins (SHBG) leading to increased levels of total circulating corticosteroids and sex steroids, respectively. Free or biologically active hormone concentrations are unchanged.
- Triglycerides may be increased and levels of various other lipids and lipoproteins may be affected.
- 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.
Last reviewed on RxList: 12/5/2008
This monograph has been modified to include the generic and brand name in many instances.
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