Uricosuric drugs are preferred for treating gout if there is not enough uric acid in the urine defined by a 24-hour collection of urine with less than 800 mg of uric acid. Uricosuric drugs are not recommended if the person has a history of renal stones. A 24-hour urine excretion of more than 800 mg indicates overproduction and xanthine oxidase inhibitors are the preferred drugs for providing treatment. Note that probenecid appears to be less effective than allopurinol.