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

There is evidence of an association between the following conditions and the use of oral contraceptives:

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

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

Changes in contraceptive effectiveness associated with co-administration of other drugs:

a. Anti-infective agents and anticonvulsants

Contraceptive effectiveness may be reduced when hormonal contraceptives are co-administered with some antibiotics, anticonvulsants, and other drugs that increase metabolism of contraceptive steroids. This could result in unintended pregnancy or breakthrough bleeding. Examples include barbiturates, rifampin, phenylbutazone, phenytoin, carbamazepine, felbamate, oxcarbazepine, topiramate, and griseofulvin.

Since desogestrel is mainly metabolized by the cytochrome P450 2C9 enzyme (CYP 2C9) to form etonogestrel, the active progestin, there is a possibility of interaction with CYP 2C9 substrates or inhibitors (such as: ibuprofen, piroxicam, naproxen, phenytoin, fluconazole, diclofenac, tolbutamide, glipizide, celecoxib, sulfamethoxazole, isoniazid, torsemide, irbesartan, losartan, and valsartan). The clinical relevance of these interactions is unknown.

b. Anti-HIV protease inhibitors

Several of the anti-HIV protease inhibitors have been studied with co-administration 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 efficacy and safety of these oral contraceptive products may be affected with co-administration of anti-HIV protease inhibitors. Health care providers should refer to the label of the individual anti-HIV protease inhibitors for further drug-drug interaction information.

c. Herbal products

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 contraceptive steroids. This may also result in breakthrough bleeding.

Increase in plasma hormone levels associated with co-administered drugs

Co-administration of atorvastatin and certain ethinyl estradiol containing oral contraceptives increased AUC values for ethinyl estradiol by approximately 20%. Ascorbic acid and acetaminophen may increase plasma ethinyl estradiol levels, possibly by inhibition of conjugation. CYP 3A4 inhibitors such as itraconazole or ketoconazole may increase plasma hormone levels.

Changes in plasma levels of co-administered drugs

Combination hormonal contraceptives containing some synthetic estrogens (e.g., 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. 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.

No formal drug-drug interaction studies were conducted with Cyclessa® (desogestrel ethinyl estradiol tablets) .

Interactions With Laboratory Tests

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

a. Increased prothrombin and factors VII, VIII, IX and X; decreased antithrombin 3; increased norepinephrine-induced platelet aggregability.

b. 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.

c. Other binding proteins may be elevated in serum.

d. Sex hormone-binding globulins are increased and result in elevated levels of total circulating sex steroids; however, free or biologically active levels either decrease or remain unchanged.

e. Triglycerides may be increased, and levels of various other lipids and lipoproteins may be affected.

f. Glucose tolerance may be decreased.

g. 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: 5/2/2007
This monograph has been modified to include the generic and brand name in many instances.