Table 9: U.S. Food and Drug Administration Pregnancy Risk Factor Definitions Category Definition A
The results of controlled studies in women fail to demonstrate a risk to the fetus in the first trimester (and there is no evidence of risk appears remote. Either the results of animal reproduction studies have not demonstrated a fetal risk but there are no controlled studies in pregnant women. OR the results of animal reproduction studies have shown an adverse effect (other than a decrease in fertility) that was not confirmed in controlled studies in women in the first trimester and there is no evidence of risk in later trimesters. Either the results of studies in animals have revealed adverse effects (teratogenic, embryocidal or other) on the fetus and there are no controlled studies in women. OR results of studies in women and animals are not available; drug should be given only if the potential benefit justifies the potential risk to the fetus.
B
C
D There is positive evidence of human fetal risk, but the benefits of use in pregnant women may be acceptable despite the risk (for example, if the drug is needed in a life-threatening situation or for a serious disease for which safer drugs cannot be used or are ineffective). X Results of studies in animals or humans have demonstrated fetal abnormalities or evidence of fetal risk based on human experience, or both, and the risk of the use of the drug in pregnant women clearly outweighs any possible benefit; use of the drug is contraindicated in women who are or may become pregnant. Note . Adapted from “Content and Format Labeling for Human Prescription Drug and Biological Products; Requirements for Pregnancy and Lactation Labeling,” by the U.S. Food and Drug Administration, 2014. Retrieve format-of-labeling-forhuman-prescription-drug-and-biological-products- requirements-for; “Drug Safety and Availability,” by the U.S. Food and Drug Administration, 2015a. Retrieved from http://www.fda.gov/Drugs/DrugS Requirements for Over-the-Counter Drugs,” by the U.S. Food and Drug Administration, 2015b. Retrieved from http://www.accessdata.fda.gov/ scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=201.80
Some antibiotics can cross the placenta and be deposited in the embryo’s teeth and bones (sites of active calcification). Members of the tetracycline drug class (tetracycline, minocycline, and doxycycline) exhibit this effect: As little as 1 gram per day of tetracycline taken during the third trimester of pregnancy produces yellow staining of both the primary and secondary teeth in the developing fetus (Lochary, Lockhart, & Williams, 1998; Tredwin, Scully, & Bagan-Sebastian, 2005). All of the tetracyclines are listed as pregnancy risk factor Category D by the FDA. Topical minocycline oral powder – indicated as an adjunct to scaling and root planing procedures for reduction of pocket depth in patients with adult periodontitis – has a black box warning to avoid use of the medication during pregnancy and in nursing women. Because all tetracyclines, including doxycycline, are excreted in breast milk, the pharmaceutical manufacturers recommend against breastfeeding while taking these medications (Pfizer Labs, 2011). However, in apparent contradiction, the American Academy of Pediatrics (AAP) considers all of these agents to be compatible with breastfeeding (AAP Committee on Drugs, 2001). Doxycycline is less bound to the calcium in maternal milk, which may lead to greater absorption compared with other tetracyclines. Only minimal amounts of doxycycline are excreted in human milk, and the relative amount of tooth staining has been reported to be lower when compared with other tetracycline analogues. On the basis of information from the results of animal studies, the progenitor manufacturer of clarithromycin has stated that this antibiotic should not be used in pregnant women except in clinical circumstances in which no alternative therapy is appropriate (Abbott Laboratories, n.d.a; Andersen et al., 2013). Clarithromycin is listed as pregnancy risk factor Category C by the FDA (Einarson et al., 1998), and although it is not known if clarithromycin is excreted in human breast milk, the manufacturer recommends that caution be exercised when administering clarithromycin to breastfeeding women (Abbott Laboratories, n.d.a; Einarson et al., 1998). Other macrolides, such as erythromycin and azithromycin, are considered compatible with breastfeeding (Abbott Laboratories, n.d.b; Pfizer Labs, 2009).
All of the other antibiotics commonly used in dentistry are classified by the FDA as pregnancy risk factor Category B (amoxicillin, azithromycin, cephalexin, clindamycin, erythromycin, metronidazole, and penicillin). All of these antibiotics are considered to be compatible with breastfeeding by the AAP, except for metronidazole, which is an in vitro mutagen; clinicians should recommend that the patient stop breastfeeding for 12 to 24 hours (pump and discard) after taking the single-dose therapy, to allow excretion. Since erythromycin is concentrated in human milk, it should be used cautiously, as there are published cases of pyloric stenosis being induced in the breastfed newborn (Sorensen et al., 2003; Stang, 1986). Although antifungal agents are not prescribed commonly by dentists, the appearance of oral thrush may at times necessitate the use of these drugs. In the case of oral thrush, oral nystatin (FDA pregnancy risk factor Category C) is the safest agent to use both in pregnant patients and in patients who are breastfeeding. Absorption after oral use is poor, greatly reducing the risk to the fetus or the breastfed newborn (Czeizel, Kazy, & Puhó, 2003). The other common indication for antifungals is for the female dental patient who develops a vaginal yeast infection secondary to one of the previously listed antibiotic treatments. Vaginal candidiasis (moniliasis or thrush) is a common and frequently distressing infection for many women, and it is even more common in pregnancy (Mashburn, 2012). The Cochrane Pregnancy and Childbirth Group Trials Register has reviewed the Cochrane Central Register of Controlled Trials (CENTRAL/CCTR) and concluded that topical treatments with either terconazole or clotrimazole are not only preferred in pregnant women, given the decreased systemic absorption, but also appear to be more effective than oral therapies such as nystatin for treating symptomatic vaginal candidiasis during pregnancy (Soong & Einarson, 2009). Patients may self-medicate, because many of these preparations are available over the counter (OTC) without a prescription. However, the Cochrane Review on this topic suggests that pregnant women may require a longer treatment than the shorter courses more commonly used in women who are not pregnant.
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