Torsemide Is Associated with Higher Levels of Urinary Biomarkers of Tubular Injury Compared to Furosemide

Introduction In patients with heart failure (HF), loop diuretics including torsemide and furosemide are a cornerstone of therapy for volume overload. Torsemide may be associated with enhanced natriuresis which could hemodynamically lead to worsening renal function (WRF). If renal hypoperfusion is persistent and severe, renal tubular injury (RTI) may occur but WRF does not always correlate with renal tubular injury. Urinary biomarker analysis can help identify when renal tubular injury occurs. Hypothesis In patients with chronic HF, use of torsemide is associated with higher biomarker levels of urinary RTI compared to furosemide. Methods Urine samples were collected from patients with chronic HF who had been treated for at least one month with furosemide (n=15) or torsemide (n=10). Urinary concentrations of the following biomarkers were compared between groups: albumin, β-2 microglobulin (β2M), CystatinC, epidermal growth factor (EGF), neutrophil gelatinase-associated lipocalin (NGAL), osteopontin (OPN), and uromodulin. Results One patient in the furosemide group had outliers in several biomarkers and was excluded from the analysis. All urinary markers were present in higher concentration in the torsemide group. Using a nonparametric Wilcoxon test, statistically significant differences were found in the distribution of urinary albumin (p=0.001), β-2M (p=0.03), and NGAL (p=.04) between the two groups. Conclusion Significantly higher levels of RTI biomarkers in the torsemide group suggest that there may be a greater degree of WRF with torsemide compared with furosemide. More significant differences between other urinary biomarkers may be seen with a greater sample size. This study was limited by sample size and inability to compare concentration of urine. Further study is warranted to explore the difference in these groups.