In some patients, the addition of a daily medicine may be recommended to decrease the risk of future stones. In clinical trials, these medications have been shown to significantly reduce the number of stones re-developed in patients with a known history of stones.
While many patients are reluctant to take medications and prefer to focus on dietary modification, medications can be a good option, especially in individuals who frequently develop new stones.
Common preventative medications
Three common medications are used in the prevention of stones.
Useful for: Low urinary citrate (hypocitraturia), renal tubular acidosis, uric acid stones, calcium oxalate stones, cystine stones.
How does it work: Potassium citrate has two beneficial effects in stone formers. It increases urinary citrate, which acts a direct inhibitor of stone formation of calcium oxalate stones. It also increases urine pH, making urine more alkaline which reduces uric acid stone formation.
How well does it work: In four randomized studies with a total of 227 patients on citrate medications or placebo, treatment reduced the recurrence of stones from 65% to 46.5% after at least one year of treatment. In two randomized studies with a total of 104 patients who were treated with citrate medication after stone surgery, the recurrence rate of stones was 72.5% in those on placebo and 34% in those on medication. (Mattle and Hess, Urol Res, 2005)
Side effects: Potassium citrate can be given in powder form for mixing in liquid, in liquid form, and as a tablet. The primary side effects of this medication is gastric irritation, less so with the tablet which contains potassium citrate in a wax matrix.
Useful for: High urinary calcium (hypercalciuria), calcium stones.
How does it work: Thiazides including hydrochlorothiazide, chlorthalidone, and indapamide, stimulate calcium reabsoprtion in the kidney, reducing the concentration of calcium in the urine.
How well does it work: Randomized trials have found a significant decrease in stone formation with the use of thiazides. In a study of 50 stone formers who received either placebo or hydrochlorothiazide 25 mg twice a day, 75% of those on treatment remained stone free as compared to 45% of the placebo group over three years. Those on treatment also had a longer stone free interval (Laruem and Larsen, Acta Med Scand, 1984).
Side effects: Thiazide treatment can cause a decrease in blood potassium levels and can also can reduce citrate levels in the urine. Therefore, potassium citrate is sometimes given with thiazides to correct both the low potassium and citrate that can occur with its use. Fatigue and dizziness and other side effects have also been reported by patients on thiazide treatment.
Useful for: Elevated urine uric acid (hyperuricosuria), uric acid stones, calcium stones
How does it work: Allopurinol interferes with the conversion of xanthine (a purine) to uric acid with a resulting decrease in uric acid levels in urine. It is more commonly used in patients with gout. Purines are found at high concentrations in meats, seafood, and beer. Uric acid in urine can directly form uric acid stones or can act as an promoter of calcium oxalate stones.
How well does it work: In a randomized study of 60 patients with high urinary uric acid and a history of calcium stones, 31% of those on treatment developed new stones over three years compared to 58% of those on placebo. Those on treatment also had a longer time before re-developing a stone (Ettinger et al, NEJM, 1986).
Side effects:Allopurinol can cause GI upset, diarrhea, and drowsiness in addition to other potential side effects.
Less commonly used preventative medications
Penicillamine is used in patients with a history of cystine stones. It binds the cystine molecule, making it more soluble in urine. This medication unfortunately has a high rate of serious side effects and few patients can tolerate it.
This medication is also used for patients with cystine stones. It works in a similar fashion to D-penicillamine in that it binds cystine making it more soluble. However, it has lower side effects, making tolerability better.
Sodium cellulose phosphate
In patients with high calcium absorption, sodium cellulose phosphate acts as a nonabsorbable binding resin which binds calcium in the gut, reducing its absorption. However, this medication had a high rate of gastrointestinal side effects and it is now rarely used.