four retinoids - retinol ( vitamin a ) , tretinoin ( retinoic acid ) , etretinate ( the ethyl ester of trimethoxymethylphenyl retinoic acid ) , and isotretinoin ( 13-cis-retinoic acid , accutane ) - have been administered orally in humans for therapeutic purposes .
C0022265
13-cis-retinoic acid
C0699581
accutane