Which drug should be avoided in patients with a history of uric acid stones or uric acid overproduction?

Which drug should be avoided in patients with a history of uric acid stones or uric acid overproduction?

• A. Allopurinol
• B. Febuxostat
• C. Probenecid
• D. Rasburicase

Answer: (C)

The key idea is that probenecid is a uricosuric agent—it works by increasing uric acid excretion in the kidneys. While that helps lower uric acid levels in some patients, it also raises the amount of uric acid passing into the urine. In someone with a history of uric acid stones or with overproduction of uric acid, this higher urinary uric acid readily crystallizes and forms stones. So this drug should be avoided in those patients. By contrast, drugs that reduce uric acid production, like allopurinol and febuxostat, or drugs that enzymatically break down uric acid, like rasburicase, do not raise urinary uric acid and can be safer choices in this context. Allopurinol and febuxostat lower the overall amount of uric acid available to crystallize, while rasburicase converts uric acid to more soluble products, helping prevent or treat hyperuricemia-related issues.

The key idea is that probenecid is a uricosuric agent—it works by increasing uric acid excretion in the kidneys. While that helps lower uric acid levels in some patients, it also raises the amount of uric acid passing into the urine. In someone with a history of uric acid stones or with overproduction of uric acid, this higher urinary uric acid readily crystallizes and forms stones. So this drug should be avoided in those patients.

By contrast, drugs that reduce uric acid production, like allopurinol and febuxostat, or drugs that enzymatically break down uric acid, like rasburicase, do not raise urinary uric acid and can be safer choices in this context. Allopurinol and febuxostat lower the overall amount of uric acid available to crystallize, while rasburicase converts uric acid to more soluble products, helping prevent or treat hyperuricemia-related issues.