Urine Orotic Acid-Orotidine Levels in Azaribine-Treated Patients with Psoriasis

Azaribine, as a pyrimidine analog, blocks the decarboxylase conversion of orotidylic acid to uridine monophosphate with a resultant excretion of accumulated orotic acid and orotidine in the urine. Patients treated with azaribine may develop transitory, severe central nervous system symptoms of depression, lethargy, and ataxia. These side effects are not predictable from oral dosage, and blood levels of the drug are very difficult to determine. All of our psoriatic patients treated with azaribine excreted large but variable amounts of orotic acid-orotidine in the urine. Spot urine ratios of orotic acid-orotidine:creatinine correlated very well with measured 24-hr urine output of orotic acid-orotidine. Patients with central nervous system symptoms were found to have very high urine levels of orotic acid orotidine. These symptoms can be prevented by monitoring the urinary orotic acid-orotidine:creatinine ratio levels and keeping them within a range which is still compatible with successful management of the psoriatic lesions.