any of a group of alkaloids that include caffeine, theophylline, and theobromine as well as the parent compound, a precursor of uric acid found in many organs of the body.
there is a genetic disease of xanthine metabolism, xanthinuria, due to deficiency of an enzyme, xanthine dehydrogenase, needed to process xanthine in the body. unchecked, xanthinuria can lead to kidney stone formation and urinary tract disease (due to xanthine stones) and to muscle disease (due to deposits of xanthine in the muscle). treatment is by avoiding foods and drinks containing xanthine derivatives, such as coffee, tea, and colas. medicinenet.com
hereditary xanthinuria type i is caused by mutations in the xdh gene. this gene provides instructions for making an enzyme called xanthine dehydrogenase. this enzyme is involved in the normal breakdown of purines, which are building blocks of dna and its chemical cousin, rna. specifically, xanthine dehydrogenase carries out the final two steps in the process, including the conversion of xanthine to uric acid (which is excreted in urine and feces). mutations in the xdh gene reduce or eliminate the activity of xanthine dehydrogenase. as a result, the enzyme is not available to help carry out the last two steps of purine breakdown. because xanthine is not converted to uric acid, affected individuals have high levels of xanthine and very low levels of uric acid in their blood and urine. the excess xanthine can cause damage to the kidneys and other tissues. medlineplus.gov
this includes individuals who have had a serious skin reaction to or otherwise "absolutely don't tolerate" allopurinol, the mainstay xanthine oxidase inhibitor for uric acid reduction, suggested steven nissen, md, of the cleveland clinic and a panelist at the meeting of the arthritis advisory committee and the drug safety and risk management advisory committee. medpagetoday.com
hydration, urine alkalinization with iv sodium bicarbonate, and allopurinol or rasburicase can prevent and treat the hyperuricemia, hyperphosphatemia, hypocalcemia, and hyperkalemia (ie, tumor lysis syndrome) caused by the rapid lysis of leukemic cells during initial therapy in all. hyperuricemia is minimized by reducing the conversion of xanthine to uric acid by giving allopurinol (a xanthine oxidase inhibitor) or rasburicase (a recombinant urate-oxidase enzyme) before starting chemotherapy. merckmanuals.com