When potent teratogens are irreplaceable drugs: Lessons of thalidomide and isotretinoin
A Pastuszak | B Burke | G Koren
Since the teratogenic effects of thalidomide became known, numerous changes have been made to the testing and marketing of new therapeutic agents intended for clinical use. Lessons learned by the scientific community following the experience with thalidomide ultimately proved advantageous in the marketing strategy of the synthetic retinoid, isotretinoin. New North American regulatory guidelines established in 1962 incorporated the elements of mandatory toxicity and reproductive studies before clinical trials. Based on this protocol, isotretinoin was confirmed as teratogenic in all animal species tested. The manufacturer acknowledged this effect well before the drug was released for clinical use in North America and developed an unprecedented educational campaign, the Pregnancy Prevention Program for isotretinoin, when it became apparent in postmarketing experience that merely labelling a teratogen as such would not prevent all cases of fetal exposure. This educational tool appears to be beneficial. With new clinical indications for thalidomide and isotretinoin recently described, the medical community may need to prepare for the potential increased use of such potent teratogens. Tools such as assays that quantify serum levels of thalidomide and isotretinoin, and effective educational programs that inform patients of the potential for birth defects may maximize the safe use of these drugs in pregnant or planning pregnancy patients. How the discovery of thalidomide as teratogenic dramatically changed the North American guidelines for reproductive and developmental toxicity testing of pharmaceuticals, and ultimately affected the clinical distribution of the known teratogen, isotretinoin, is described.