There are several drugs associated with causing birth defects in pregnant women. And, in August, the FDA announced yet another one. They informed the public in August 2011 that treatment with chronic, high doses (400-800mg/day) of Diflucan (fluconazole) during the first trimester of pregnancy may be associated with a rare and distinct set of birth defects in infants.
Fluconazole is used to treat fungal infections, including yeast infections of the vagina, mouth, throat, esophagus (tube leading from the mouth to the stomach), abdomen (area between the chest and waist), lungs, blood, and other organs. Fluconazole is also used to treat meningitis (infection of the membranes covering the brain and spine) caused by fungus. Fluconazole is also used to prevent yeast infections in patients who are likely to become infected because they are being treated with chemotherapy or radiation therapy before a bone marrow transplant (replacement of unhealthy spongy tissue inside the bones with healthy tissue). Fluconazole is in a class of antifungals called triazoles. It works by slowing the growth of fungi that cause infection.
There are several case reports published in the medical literature that describe rare and distinct congenital anomalies in infants whose mothers were treated with chronic high-dose (400-800 mg/day) fluconazole for fungal infections in the first trimester of pregnancy. Four reports involved maternal use of chronic high-dose intravenous fluconazole for coccidioidal meningitis and one report involved a human immunodeficiency virus (HIV)-positive mother who received chronic high-dose oral fluconazole for vaginal candidiasis. Cases associated with high-dose fluconazole use all shared some characteristics with the autosomal recessive genetic disorder known as Antley-Bixler syndrome. This combination of congenital anomalies occurs rarely in the general population, and is similar to anomalies seen in animals following in utero fluconazole exposure.
Chronic high-dose fluconazole may be teratogenic in humans when used in the first trimester of pregnancy; however, the magnitude of this potential human teratogenic risk is unknown. The five reports of distinct and rare congenital anomalies following chronic, high-dose in utero exposure to fluconazole suggest a possible drug threshold effect for a fluconazole embryopathy.
The available data in the medical literature does not suggest an association between low-dose oral fluconazole use in the first trimester of pregnancy and congenital anomalies. The few published epidemiological studies of in utero exposure to low doses of fluconazole (most patients received a single oral dose of 150 mg) showed no consistent pattern of anomalies among affected infants; however, most of these studies were too small to accurately detect an increased risk for major birth defects overall. In addition, none of these studies were large enough to accurately detect an increased risk for a rare or unique birth defect or syndrome.
Based on this information, the pregnancy category for fluconazole indications (other than vaginal candidiasis) has been changed from category C to category D. The pregnancy category for a single, low dose of fluconazole has not changed and remains category C.
Pregnancy category D means there is positive evidence of human fetal risk based on human data but the potential benefits from use of the drug in pregnant women with serious or life-threatening conditions may be acceptable despite its risks.
Healthcare professionals should counsel patients if the drug is used during pregnancy or if a patient becomes pregnant while taking the drug. Patients should notify their healthcare professionals if they are or become pregnant while taking fluconazole. If a patient uses fluconazole during pregnancy, the patient should be informed of the potential risk to the fetus.