Challenges for the Future

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Chapter: Pharmacovigilance: Drug Safety in Pregnancy

One area of opportunity is improvement in the designs of pre-marketing reproductive toxicity studies.


Existing  methods of pharmacovigilance for medication-induced birth defects, taken individually or as a whole, are limited in capacity to recognize a potential teratogenic effect with a new pharmaceutical agent or, conversely, to provide reassurance that a new drug does not pose a substantial risk. These limitations are amplified if the drug is infrequently used by women of reproductive age, if the relative risk for congenital anomalies is not high or if the associated birth defect(s) pattern is not unique, is difficult to diagnose or is not likely to be recognized at birth. Existing methods also suffer from the need for large enough sample sizes and the costs associated with supporting studies that are adequately powered.

One area of opportunity is improvement in the designs of pre-marketing reproductive toxicity studies. If the cross-species predictive value of these experiments can be increased, then it may be possi-ble in the pre-clinical setting to accurately identify and avoid human pregnancy exposure to those agents that will be new teratogens (Moore et al., 1995; Lau et al., 2000; Selevan, Kimmel and Mendola, 2000). Another possibility for the future is to take advan-tage of the efficiency and cost-effectiveness of large existing databases to ‘screen’ for possible signals of major teratogenic effects of new and older medica-tions. When strong signals are identified, other meth-ods, such as case–control surveillance studies or small follow-up studies, might be appropriate for confirma-tion or refutation.

However, it is important to recognize that no single study design or methodology is sufficient to assure that new teratogens will be identified in a timely fash-ion or that medications that can be used relatively safely in pregnancy are also identified as quickly as possible. Therefore, a coordinated and systematic approach to evaluating new medications, both on a national and on an international basis, could contribute to more effective pharmacovigilance for birth defects and provide information that is critically and urgently needed by clinicians and pregnant women (Olsen et al., 2002; Mitchell, 2003). The coordinated and integrated use of existing ongoing resources includ-ing adverse event reporting, large databases, popu-lation cohort studies and case–control surveillance along with the additional complementary information provided by pregnancy registries and small cohort studies would require substantial efforts toward the harmonization of purposes and methods. However, a comprehensive systematic surveillance system offers far more promise for effective pharmacovigilance than the fragmented and often sporadic methods that are currently in place to evaluate drug safety for preg-nant women and their infants. With the large number of prescription and over-the-counter medications used by pregnant women, a teratogen surveillance system that can adequately address these safety issues could substantially reduce the uncertainty around the safety of medications used during pregnancy.

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