Phosphorus Content of Commonly Prescribed Medications Among Patients With Chronic Kidney Disease.

Objectives: This study aimed to build a brand-specific library of phosphorus content in medications and to determine the median daily phosphorus intake from medications among chronic kidney disease (CKD) patients in Singapore.

Methods: This is a single-center, cross-sectional study conducted in 200 patients with CKD Stages 3-5D. Package inserts of medications commonly used by the CKD patients were reviewed to identify brands containing phosphorus. Drug manufacturers were contacted to obtain phosphorus content of products. The median daily phosphorus intake from medications of the 200 patients was then calculated using the information.

Results: A total of 399 formulations of 204 medications and supplements were reviewed (March 2020). Fifty-eight (15%) formulations were found to contain phosphorus. Forty-three (11%) formulations had missing information regarding the phosphorus content. Based on available information, the median daily phosphorus intake from medications was 1.28 mg (interquartile range = 0.006-16.08) across the CKD stages. Patients with CKD Stage 5D had a higher median intake of 4.09 mg (P = .009). A dose-independent variation in phosphorus content of excipients between generic and branded formulations was noted in this study. We have developed a library of phosphorus content in medications.

Conclusions: The inorganic phosphorous content in frequently prescribed medications for CKD patients is generally low, with excipients (as opposed to the active ingredient or counterions) being the main source of phosphorus. Although this may seem almost negligible in comparison to the recommended dietary intake, prescribers should still exercise care, given the wide range of phosphorus content possible between different brands of the same medication, and the unpredictable absorption of inorganic phosphate in CKD patients.