There are many drugs on the world market that are contraindicated during pregnancy, as they can cause developmental abnormalities in the fetus. In preclinical and clinical phases of evaluating new drugs, tests of reproductive and developmental toxicity are carried out, which determine the effects of the drugs on the embryo or fetus. Since these tests are in most cases carried out on animal models, scientists have been developing alternative testing methods in recent decades that would reduce the use of animals. The purpose of this thesis is to review the guidelines on new drug testing for reproductive and developmental toxicity, to review alternative in vitro methods used for testing and examine the selection of medicines contraindicated in pregnancy and their mechanisms of toxic action on the fetus.
Recommendations for drug testing for reproductive and developmental toxicity are set out in ICH S5 (R3) guideline. To review alternative testing methods, we used scientific articles from the PubMed database, using search profile "(reproductive OR developmental) AND toxicity AND testing AND alternative methods" and restrictions: research in English, review articles and systematic articles from 2017–2022. Medicines contraindicated in pregnancy were examined in the eMedExpert and MPR databases, and the mechanisms in the Google Scholar database, with the search profile " active substance in English" and "teratogenic mechanism", "teratogenicity" and "mechanism of reproductive toxicity".
Testing guidelines include information on testing strategies, test types, timeframes, and testing goals. Since most of the world's experimental animals are used in developmental toxicity studies, in vitro methods are used, the most famous being rodent whole embryo culture test, mouse embryonic stem cells test and zebrafish. Among many medicinal substances that are contraindicated in pregnancy, we have selected 14 available on the Slovenian market. The mechanisms of their teratogenic action are folate antagonism, neural crest cell disruption, endocrine disruption, oxidative stress, vascular disruption, and teratogenesis mediated by specific receptors or enzymes e. g. HMG-CoA reductase.
Alternative testing methods have been widely used in recent years, but they will not be able to replace classic animal testing for a long time, and the more detailed mechanisms of teratogenicity are still a big unknown due to their complexity.
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