American Board of Internal Medicine (ABIM) Certification Practice Exam

What medications may be prescribed to patients with recurrent uric acid stones despite other treatments?

1. Xanthine oxidase inhibitors

2. Diuretics

3. Antibiotics

4. Calcium channel blockers

The correct answer is: Xanthine oxidase inhibitors

In cases of recurrent uric acid stones, xanthine oxidase inhibitors are prescribed as they specifically target the underlying cause of uric acid stone formation. These medications work by reducing uric acid levels in the blood and urine, which can help prevent the formation of these types of stones. Uric acid stones form when there is an excess of uric acid in the urine, which can occur in patients with conditions that lead to increased purine metabolism. By inhibiting xanthine oxidase, these medications decrease the production of uric acid, leading to lower levels in the urine. This reduction helps to prevent the crystallization of uric acid, thereby reducing the risk of stone recurrence. In contrast, while diuretics can be helpful in managing certain types of kidney stones, they do not address the specific metabolic issue associated with uric acid stones. Antibiotics have a role in preventing infections but do not influence stone formation directly. Calcium channel blockers are generally used for hypertension and certain cardiac conditions and do not play a significant role in stone prevention or management. Therefore, xanthine oxidase inhibitors are the most appropriate and effective treatment for patients with recurrent uric acid stones.