Risk classification for drug use during pregnancy.

Introduction: In many countries, risk classification systems have been set up to summarize the sparse data of drug safety during pregnancy. But, these have resulted in ambiguous statements that are often difficult to compare, interpret and use with accuracy when counseling patients on drug use in pregnancy. The objective of this study was to compare and analyses the correlation and consistency between and the criteria for risk classification for medications used during pregnancy. Materials and Methods: Risk classification systems from the US Food and Drug Administration (FDA), the Australian Drug Evaluation Committee (ADEC) and the Swedish Catalogue of Approved Drugs (FASS), were evaluated, reviewed and compared on basis of the risk factor typology to which they had been assigned. Also, evidence on teratogenicity and adverse effects during pregnancy was retrieved using Medline. Results: Risk factor category allocation for 645 drugs classified by the FDA, 446 classified by ADEC and 527 classified by FASS was compared. Only 61 (26%) of the 236 drugs common to all 3 systems were placed in the same risk factor category. Analysis of studies on the safety of common drugs during pregnancy of drugs classified as X by the FDA showed that the variability in category allocation was not only attributable to the different definitions for the categories. Conclusion: Differences in category allocation for the same drug can be a source of great confusion among users of the classification systems as well as for those who require information regarding risk for drug use during pregnancy. [ABSTRACT FROM AUTHOR]