Pharmaceutical versus Over-the-Counter Potassium Citrate: A Benchtop Comparison

Abstract

Introduction: Potassium citrate has been shown to significantly reduce kidney stone recurrence by alkalinizing urine and increasing citrate excretion. However, the cost of potassium citrate can be prohibitive. Thus, over-the-counter use of potassium citrate supplements has gained interest from patients and providers due to reported decreased cost. Prior studies show that fluids such as orange juice, Crystal Light and certain sodas are reasonable sources of alkali citrate; however, the true alkali citrate content among leading over-the-counter supplements is unknown. We investigate popular supplements and compare them to pharmaceutical potassium citrate.

Methods: The top 6 potassium citrate supplements were purchased from Amazon.com in October 2020 and April 2021. These supplements and Urocit®-K were dissolved in deionized water and diluted before measurement with a colorimetric citrate assay kit. A pH electrode was used to measure the pH of each sample and the alkali citrate content of each supplement was calculated.

Results: Urocit-K and Thorne® had the highest percentage of alkali citrate per gram. NOW® supplements and Nutricost® offered the cheapest alkali citrate at less than 1 cent per mEq.

Conclusions: Citrate supplements vary widely in their cost and citrate content. Patients and providers may find this information useful depending on their individual preferences for cost and pill size. Pharmaceutical Urocit-K was not the most cost-effective option; however, it may be the more convenient option as it requires fewer pills.

Keywords: costs and cost analysis; kidney; nephrolithiasis; urolithiasis.