Preventive medication

When medication is considered

Preventive tablets are not for every stone former. They are most useful for:¹

• Patients with two or more stones.
• Patients with a specific metabolic abnormality identified on 24-hour urine.
• Patients with uric acid, cystine or struvite stones.
• Stone formers who have already optimised hydration and diet without effect.

The first step is therefore a metabolic workup - 24-hour urine studies, fasting bloods, and where possible stone composition analysis. Treatment is guided by the findings rather than prescribed blind.

Potassium citrate

Potassium citrate raises urinary citrate (a natural inhibitor of crystallisation) and raises urinary pH (making uric acid and cystine more soluble). It is the most broadly useful preventive medication.¹

• Indications: calcium stones with low urinary citrate; calcium stones with persistently acidic urine; all uric acid stones (for both dissolution and prevention); cystine stones.
• How it is given: typically 40-60 mEq a day in divided doses, as tablets or liquid. Dose is titrated to urine pH (target 6.5-7.0 for most indications; 7.0-7.5 for cystine).
• Common side-effects: mild gastrointestinal upset; occasionally reflux. Taking with food improves tolerability.
• Monitoring: home urine pH testing with dipstick strips; periodic blood potassium in at-risk patients.
• Cautions: patients with kidney failure, uncontrolled diabetes, or on potassium-sparing diuretics need careful supervision.

Thiazide diuretics

Thiazides (bendroflumethiazide, hydrochlorothiazide, chlorthalidone, indapamide) reduce urinary calcium excretion - useful in calcium stone formers with hypercalciuria on 24-hour urine.¹

• Indications: recurrent calcium oxalate or calcium phosphate stones with a high 24-hour urinary calcium.
• How it is given: usually once daily in the morning.
• Common side-effects: mild increase in blood glucose, low potassium, rare reduced libido. Often pairs well with potassium citrate (which replaces the lost potassium and adds urinary citrate).
• Monitoring: urea, electrolytes and glucose a few weeks after starting and periodically thereafter.

Allopurinol

Allopurinol reduces the production of uric acid by blocking the enzyme xanthine oxidase.

• Indications: recurrent uric acid stones, and calcium oxalate stone formers with high urinary uric acid.¹
• How it is given: 100-300 mg once daily, titrated to serum and urinary uric acid.
• Common side-effects: rash (usually mild - occasionally a rare severe allergic reaction in HLA-B*58:01-positive patients of Asian ancestry), mild liver function changes.
• Monitoring: full blood count, liver function and renal function periodically.

Thiol-binding drugs for cystine stones

Tiopronin and D-penicillamine form soluble complexes with cystine and are used in severe cystinuria when hydration and alkalinisation are insufficient. They have significant side-effects (rash, taste disturbance, low blood counts, proteinuria) and require specialist renal medicine supervision.¹

Targeted antibiotics for struvite stones

Struvite stone disease needs eradication of the underlying urinary infection. After complete surgical clearance, selected patients may be treated with culture-directed antibiotic courses or long-term methenamine hippurate to reduce bacterial growth.¹ See the struvite stones page.

Other considerations

• Calcium supplements can increase stone risk if taken between meals. Discuss with your GP whether you need them at all, and take with food if you do.
• High-dose vitamin C (> 1 g/day) can increase urinary oxalate and should be avoided in calcium oxalate stone formers.
• Vitamin D is important for bone health and generally safe; occasional stone formers have elevated urinary calcium on supplementation and may need their dose reviewed.

The practical pathway

1. Metabolic workup

   Two 24-hour urine studies, fasting bloods, stone composition analysis if available.

2. Tailored prescription

   Medication chosen on the basis of the findings and the stone type. Often organised with a partnering renal physician.

3. Follow-up urine

   Repeat 24-hour urine at 6-12 weeks to confirm the medication has achieved its biochemical target.

4. Long-term review

   Annual or biennial clinic review with periodic imaging. Medication dose is adjusted as needed.

Related pages

Reference

1. Skolarikos A, et al. EAU Guidelines on Urolithiasis. European Association of Urology; 2025.