Anemia of azaribine in the treatment of psoriasis.

Azaribine is an effective agent in the treatment of psoriasis. In this investigation the extent of clinical dermatologic remission appeared to correlate with the degree of metabolic block induced by 6-azauridylic acid, as quantitated by the urinary excretion of orotic acid and orotidine, and the development of anemia. Following azaribine therapy there was a coordinate rise of the specific activities of erythrocyte orotate phosphoribosyltransferase and orotidine-5'-monophosphate decarboxylase. There was no correlation between the pretreatment activity of these enzymes and the clinical response to azaribine. The anemia of azaribine therapy was mile and of a megaloblastic type. Uridine effectively corrected the azaribine-induced anemia, but led to exacerbation of the patients' psoriasis. Following uridine therapy there was a reduction in the urinary excretion of orotic acid and orotidine, presumable reflecting end-product inhibition or repression of the first steps of a repeated pyrimidine biosynthesis.