Presentation Authors: Kohldon Boydston*, Brenton Winship, Russell Terry, Leah Davis, Michael Lipkin, Glenn Preminger, Sarah Yttri, Durham, NC
Introduction: Patients with low urine pH or hypocitraturia and nephrolithiasis benefit from medical treatment with potassium citrate (KCIT). Many patients cannot take KCIT due to side effects or cost. In these patients, we have prescribed potassium bicarbonate or sodium bicarbonate as alternative alkalinizing agents (AA), though their efficacy in treating these metabolic abnormalities is unclear. We sought to determine if AA prescribed to recurrent stone formers led to similar changes in 24-hour urine pH and citrate compared to KCIT.
Methods: We performed a retrospective cohort study of adult stone formers seen from 2000-2018 with available 24-hour urine analyses. Demographics, medical history, and medications were abstracted. Two analyses were performed. The first included patients with baseline low urine pH ( < 6.0) or hypocitraturia ( < 450 mg men, < 550 mg women) off of any alkalinizing medications, who were subsequently treated with either KCIT or AA. Primary outcomes were median change in urinary pH and citrate on 24-hour urine collection after therapy. The second analysis compared the pH and citrate in patients changing from KCIT to an AA before and after the transition in a paired analysis. Comparisons were made using Wilcoxon rank sum and Wilcoxon signed rank tests. Cost savings percentages were calculated using per-pill GoodRx medication prices as of October 2018.
Results: In the first analysis, 482 KCIT and 70 AA patients were identified. Patients on AA had statistically significant differences in baseline demographics, including a lower diabetes prevalence, older age, and lower starting pH and citrate. The median increase in pH from baseline was 0.64 for KCIT and 0.51 for AA (p=0.077), and the median increase in citrate from baseline was 231 mg for KCIT and 171 mg for AA (p=0.109). In the second analysis, 71 patients were identified. The median changes in pH and citrate when switching from KCIT to an AA were -0.02 (p=0.641) and 15.91 (p=0.989), respectively. GI upset (32%), hyperkalemia (21%), cost (21%), and pill size/taste (9%) were the most common reasons cited for switching to an AA. AA represented a per-pill cost savings of 83-96% compared to KCIT.
Conclusions: Alternative alkalinizing agents lead to significant cost-savings and comparable improvements in 24-hour urine pH and citrate compared to KCIT, the standard of care. These findings confirm that there are several options available to recurrent stone formers requiring long-term metabolic therapy.