environmental agents including ethanol , 13-cis retinoic acid ( ra , accutane ) , the antimetabolite methotrexate , periods of hypoxia , ionizing radiation or hyperthermic stress , when administered acutely to pregnant experimental animals , induce stage-dependent craniofacial malformations comparable to those in corresponding human teratogen syndromes .
C0022265
13-cis retinoic acid
C0699581
accutane