Effects of a commercial lemonade beverage, potassium citrate, and combination therapy on urinary stone risk parameters in hypocitraturic stone formers: a randomized crossover trial.

BACKGROUND: Potassium citrate (KCit) is commonly prescribed to patients with recurrent nephrolithiasis; however, medication compliance is poor due to gastrointestinal side-effects. Crystal Light® (CL) sugar-free lemonade is a low-calorie beverage alternative that has been shown to increase urinary citrate and pH levels. In this study, we aimed to compare the effects of KCit, CL, and CL + KCit on 24-hour urine collections in hypocitraturic stone formers. METHODS: We performed a randomized crossover trial of 8 patients with isolated hypocitraturia on 24-hour urine collections. Patients completed three 1-week trials of KCit (15 mEq daily), CL (1 L daily), and combination CL and KCit (500 mL + 10 mEq daily) followed by immediate 24-hour urine collections after each weekly treatment. There was a washout period of 1 week in between each regimen. Statistical analysis was conducted with Kruskal-Wallis rank sum tests and linear mixed-effects models. RESULTS: The CL regimen led to the greatest increases in urinary volume (CL: 0.53 vs. KCit: -0.08 vs. CL + KCit: 0.21 L, P=0.5) and combination regimen had the greatest increase in urinary citrate (CL: 172 vs. KCit: 68 vs. CL + KCit: 173, P=0.8) from baseline. However, these differences did not reach statistical significance. The CL regimen led to a mean increase in pH of 0.42 compared to 0.25 with CL + KCit and 0.18 with KCit (P=0.6). There were similar increases in supersaturation (SS) of calcium phosphate in all regimens (CL: 0.2 vs. KCit: 0.08 vs. CL + KCit: 0.22, P>0.9). The SS of calcium oxalate (CaOx) decreased by 0.15 in the CL regimen and 1.39 in the KCit regimen but showed slight increases in the combination regimen (0.47, P>0.9). On pairwise comparison after linear mixed effects models were performed, CL resulted in a significantly greater reduction in SS uric acid compared with KCit (mean difference =-0.49, P=0.002). CONCLUSIONS: In this limited study in active stone formers with hypocitraturia, consumption of a low-calorie sugar-free citrate-containing lemonade beverage was well tolerated with no reported adverse effects. Multi-institutional studies are needed to determine clinical significance. TRIAL REGISTRATION: ClinicalTrials.gov NCT05389995.