Kidney Stone Preventive Medication
For calcium oxalate stones with hypocitraturia, start potassium citrate 30-60 mEq/day (divided doses with meals), and for uric acid stones, potassium citrate is first-line therapy at 30-80 mEq/day targeting urinary pH 6.0-6.5, while thiazide diuretics should be added for hypercalciuric calcium stone formers. 1, 2
Calcium Oxalate Stone Prevention
First-Line: Potassium Citrate
Initiate potassium citrate for patients with hypocitraturia (urinary citrate <320 mg/day) 1, 3
- Severe hypocitraturia (<150 mg/day): Start 60 mEq/day divided as 30 mEq twice daily or 20 mEq three times daily with meals 3
- Mild-moderate hypocitraturia (>150 mg/day): Start 30 mEq/day divided as 15 mEq twice daily or 10 mEq three times daily with meals 3
- Maximum studied dose is 100 mEq/day; higher doses should be avoided 3
Potassium citrate benefits even patients with normal citrate but low urinary pH 1, 2
The medication increases urinary citrate (inhibits calcium oxalate crystallization) and raises urinary pH, reducing stone supersaturation 1, 4
Prospective RCTs demonstrate 85% reduction in stone recurrence risk with potassium citrate therapy 1, 5
Add Thiazide Diuretics for Hypercalciuria
- Thiazides are indicated when 24-hour urinary calcium is elevated (>200 mg/day in women, >250 mg/day in men) 6, 7
- Thiazides reduce urinary calcium excretion and stone recurrence 6
- When patients continue forming stones despite thiazide therapy, add potassium citrate 30-60 mEq/day, particularly if hypocitraturia develops during thiazide treatment 1
Critical Pitfall to Avoid
- Never use sodium citrate instead of potassium citrate—sodium loading increases urinary calcium excretion and worsens stone risk 1, 6
Uric Acid Stone Prevention
First-Line: Potassium Citrate (NOT Allopurinol)
- Potassium citrate is first-line therapy for uric acid stones at 30-80 mEq/day (typically 60 mEq/day) 1
- Target urinary pH of 6.0-6.5 to dissolve existing stones and prevent new formation 1, 8
- Most uric acid stone formers have low urinary pH (<5.5) as the predominant risk factor, not hyperuricosuria 1, 8
When to Use Allopurinol
- Allopurinol should NOT be offered as first-line therapy because reducing uric acid excretion will not prevent stones in patients with acidic urine 1
- Reserve allopurinol for hyperuricosuric patients (>800 mg/day in men, >750 mg/day in women) with recurrent uric acid stones who fail alkalinization therapy 9, 8
Essential Dietary Modifications (All Stone Types)
- Increase fluid intake to achieve urine volume ≥2.5 liters daily 1, 6, 3
- Limit sodium to <2,300 mg/day to reduce urinary calcium excretion 1, 6
- Maintain normal dietary calcium intake of 1,000-1,200 mg/day—restricting calcium paradoxically increases stone risk by raising urinary oxalate 1, 6
- Increase fruits and vegetables for natural alkali load 2, 6
Monitoring Protocol
Initial Assessment
- Obtain 24-hour urine collection on random diet to identify metabolic abnormalities (calcium, citrate, oxalate, uric acid, pH, volume) 6
- Perform stone analysis at least once to confirm composition 6
Follow-Up Monitoring
- Reassess at 6 months with 24-hour urine testing and serum electrolytes (potassium, sodium, creatinine) 1, 3
- Continue annual monitoring thereafter with more frequent checks if stone activity persists 1
- Check serum potassium periodically as potassium citrate can cause hyperkalemia, especially with renal insufficiency 3
- Perform periodic ECGs in patients on potassium citrate 3
Treatment Duration
- Continue potassium citrate indefinitely as long-term therapy for patients with persistent metabolic risk factors 1, 2
- Uric acid stone formers typically require lifelong alkalinization since low urinary pH is usually permanent 1
- Only consider discontinuation after several years stone-free with normalized metabolic parameters, followed by close monitoring 1
- Resume therapy immediately if stones recur after stopping 1