What medications are used to treat renal stones?

Medications for Renal Stone Treatment

Medication selection for renal stones should be tailored to the specific stone type, with potassium citrate being the first-line therapy for uric acid and cystine stones, and thiazide diuretics with/without potassium citrate for calcium stones. 1, 2

Stone-Specific Pharmacological Management

Calcium Stones

• Thiazide diuretics are recommended for patients with recurrent calcium stones, particularly those with hypercalciuria 1, 2
• Potassium citrate is indicated for patients with low urinary citrate or those with persistent stone formation despite addressing other metabolic abnormalities 1, 3
• Allopurinol should be offered to patients with recurrent calcium oxalate stones who have hyperuricosuria and normal urinary calcium 1
• Combination therapy with thiazides and potassium citrate may be necessary for patients with persistent stone formation 2

Uric Acid Stones

• Potassium citrate is the first-line therapy for uric acid stones to raise urinary pH to approximately 6.0 1, 4
• Allopurinol should not be routinely offered as first-line therapy for uric acid stones as most patients have low urinary pH rather than hyperuricosuria as the predominant risk factor 1
• Potassium citrate therapy has been shown to significantly reduce stone formation in patients with uric acid lithiasis 4

Cystine Stones

• Potassium citrate should be offered to raise urinary pH to approximately 7.0 1
• Cystine-binding thiol drugs, such as alpha-mercaptopropionylglycine (tiopronin), should be offered to patients unresponsive to dietary modifications and urinary alkalinization 1
• Tiopronin is preferred over d-penicillamine due to better efficacy and fewer adverse events 1

Struvite Stones

• Urease inhibitors (acetohydroxamic acid or AHA) may be beneficial for patients with struvite stones, though side effects may limit use 1
• Antibiotic therapy is necessary to address the underlying urease-producing bacterial infection 5

Medication Dosing and Considerations

Potassium Citrate

• Typical dosing ranges from 30 to 100 mEq per day, usually administered as 20 mEq three times daily 4
• Potassium citrate is preferred over sodium citrate, as sodium load may increase urine calcium excretion 1
• FDA-approved indications include renal tubular acidosis with calcium stones, hypocitraturic calcium oxalate nephrolithiasis, and uric acid lithiasis with or without calcium stones 4

Thiazide Diuretics

• Hydrochlorothiazide has traditionally been dosed at 25-50 mg daily for stone prevention 6
• Chlorthalidone 25 mg daily may be more effective than hydrochlorothiazide at equivalent doses, producing greater reduction in urinary calcium (41% vs 21%) 7
• Recent evidence suggests that the efficacy of hydrochlorothiazide in preventing stone recurrence may be limited compared to historical data 8

Monitoring and Follow-up

• Obtain a 24-hour urine specimen within six months of initiating treatment to assess response to therapy 1
• Annual 24-hour urine collections are recommended for ongoing monitoring, with more frequent testing depending on stone activity 1
• Monitor serum potassium levels, particularly in patients on thiazide diuretics or potassium citrate 7

Common Pitfalls and Caveats

• Inadequate fluid intake remains a major risk factor for stone recurrence regardless of pharmacological intervention 2
• Dietary calcium restriction should be avoided as it can worsen stone formation 2
• Low-dose thiazides (12.5 mg) may not significantly lower urinary calcium and may be insufficient for stone prevention 7
• Combination therapy may be necessary for patients with multiple metabolic abnormalities 1, 2