A well-accepted strategy to prevent
kidney stones is to increase urine volume by increasing oral intake of fluids, especially water, to lower supersaturation of the relevant, relatively insoluble
salts, and thereby lower the risk of precipitation. Randomized controlled trials have shown that this strategy works. It is inexpensive, safe, and intuitively attractive to patients. However, although any beverage can increase urine volume, and citrus juices can increase urine
citrate content and pH, no beverage other than water has been clearly shown by randomized controlled trial to prevent
kidney stones. We designed an innovative, palatable, low-calorie, high
alkali citrate beverage to prevent
kidney stones, called Moonstone. One packet of Moonstone
powder, mixed in 500 ml of water, contains 24.5 meq of
alkali citrate. We administered one packet twice a day to ten
calcium stone formers. Moonstone resulted in an increase in mean 24-h urine
citrate and urine pH, and a decrease in supersaturation of
calcium oxalate in
calcium stone formers compared to an equal volume of water. These changes, comparable to those seen in a prior study of a similar amount of (
potassium-magnesium) citrate, will likely be associated with a clinically meaningful reduction in
kidney stone burden in patients with
calcium stones. The effect to increase urine pH would also be expected to benefit patients with
uric acid and
cystine stones, groups that we hope to study in a subsequent study. The study preparation was well tolerated and was selected as a preferred preventative strategy by about half the participants. Moonstone is an alternative, over-the-counter
therapy for
kidney stone prevention.