“…The toxic ef fects of orally administered 13cRA are: chelitis, headache, xerosis, anorexia, dry mucous membranes, nausea and vomiting, and to a lesser degree visual disturbance, pruritis, and hair thinning [7,8], Although topical tRA therapy is regarded safe [9,11,12], orally administered tRA, 13cRA and etretinate are highly teratogenic. Thus, these drugs are not prescribed to women who are pregnant or might become pregnant during therapy [1,[13][14][15][16][17], All-/ram-retinoyl (3-glucuronide (RAG), first identified as a biliary metabolite of vita min A [18,19], occurs endogenously in hu man blood [20], RAG and its 13-m-isomer have been identified as major biliary metabo lites of RA in the rat [21][22][23], Following administration of all-tram, 13-d,v-and 9-cis-RA. their respective p-glucuronides have been characterized as major plasma metabolites in the monkey [24][25][26], in the rat [27,28], in the mouse [27,29], in the rabbit [30], and in the human [20,25], RAG, like RA, shows high biological activity in enhancing the growth of vitamin A-deficient rats [31,32] and in induc ing the differentiation of HL-60 [33][34][35][36] and GBA-HAN-1C cells [37], In contrast.…”