Potassium Citrate Indications by Stone Type
Potassium citrate is prescribed for calcium stones (both calcium oxalate and calcium phosphate), uric acid stones, and cystine stones, with specific indications varying by the underlying metabolic abnormality and urinary chemistry.
Primary Indications
Calcium Stones (Calcium Oxalate and Calcium Phosphate)
Potassium citrate should be offered to patients with recurrent calcium stones who have hypocitraturia (low urinary citrate excretion). 1 The AUA guidelines provide Grade B evidence supporting this recommendation based on prospective RCTs demonstrating reduced stone recurrence. 1
Additional calcium stone scenarios where potassium citrate is indicated:
- Calcium stone formers with normal citrate but low urinary pH may also benefit from citrate therapy 1
- Calcium phosphate stone formers with hypocitraturia should receive potassium citrate because citrate is a potent inhibitor of calcium phosphate crystallization 1
- Recurrent calcium stones when other metabolic abnormalities have been addressed but stone formation persists 1
- Hypocitraturic calcium oxalate nephrolithiasis of any etiology per FDA labeling 2
Uric Acid Stones
Potassium citrate is first-line therapy for uric acid stones to alkalinize urine and raise pH to 6.0. 1 This is critical because most uric acid stone formers have low urinary pH rather than hyperuricosuria as the predominant risk factor. 1
- Allopurinol should NOT be offered as first-line therapy since reducing uric acid excretion will not prevent stones in patients with unduly acidic urine 1
- FDA-approved for uric acid lithiasis with or without calcium stones 2
Cystine Stones
Potassium citrate should be offered to raise urinary pH to 7.0 in cystine stone formers. 1 The increased pH enhances cystine solubility. 1
- This is part of first-line therapy along with increased fluid intake and dietary sodium/protein restriction 1
- If these modifications are insufficient, cystine-binding thiol drugs (tiopronin) constitute the next line of therapy 1
Renal Tubular Acidosis (RTA) with Calcium Stones
Potassium citrate is FDA-approved for management of RTA with calcium stones. 2 These patients typically have hypocitraturia as part of their metabolic derangement. 3
Key Mechanistic Considerations
The therapeutic effects of potassium citrate work through multiple mechanisms:
- Increases urinary citrate, which inhibits calcium oxalate and calcium phosphate crystallization 1, 4
- Raises urinary pH through alkali load, increasing solubility of uric acid and cystine 1
- Decreases urinary saturation of calcium oxalate and reduces propensity for spontaneous nucleation 5, 3
- Preferred over sodium citrate because sodium load may increase urinary calcium excretion 1
Important Clinical Pitfalls
Potassium citrate is NOT indicated for struvite (infection) stones, which require treatment of the underlying urease-producing organism. 1 The guidelines make no mention of citrate therapy for this stone type.
Monitor for hyperkalemia, particularly in patients with impaired potassium excretion mechanisms—this is a contraindication per FDA labeling. 2
Follow-up 24-hour urine testing should be obtained within 6 months of initiating treatment to assess metabolic response, then annually or more frequently depending on stone activity. 1