Pseudo-Worsening of Kidney Function Due to Inhibition of Renal Creatinine Secretion: Quality of Information Provided in Prescribing Information/SmPC.

Abstract

Determination of serum creatinine concentrations and subsequent calculation of estimated glomerular filtration rates (eGFR) is a cornerstone of clinical medicine. Crucial clinical decisions such as drug treatment discontinuations are based on eGFR calculated from serum creatinine measurements. However, creatinine is not only filtered in the kidneys, but also actively secreted into urine. Creatinine transporters such as OCT2, OCT3, MATE1, MATE2-K, and OAT2 expressed in proximal tubular cells are responsible for active renal secretion of creatinine. Multiple drugs (e.g., oral antitumor drugs) inhibit these transporters thereby causing a pseudo-worsening of kidney function with an increase in serum creatinine concentrations and a decrease in eGFR while other methods for eGFR determination (e.g., by cystatin C) reveal normal kidney function. Since US Prescribing Information (PI) and European Summaries of Product Characteristics (SmPCs) are the most relevant source of information for physicians, we investigated the quality of information in US PI/German SmPCs of drugs with clear evidence for pseudo-worsening of kidney function. 514 drugs putatively interacting with creatinine transporters were identified. For 149 of those drugs, an increase in serum creatinine concentrations has been described. Available data confirmed the existence of pseudo-worsening of kidney function for 30 of those drugs, for the remaining 119 drugs existing data are insufficient. Only 23.5% (12/51) of the 30 drugs' PI/SmPCs contained unambiguous statements on this proven pseudo-worsening of kidney function and gave clear recommendations for clinical management. Taken together, inadequate information provided in PI or SmPCs on the pseudo-worsening of kidney function poses patients at unnecessary risks.