The Effects of Enalapril on Urinary Protein Excretion in Patients with Idiopathic Membranous Nephropathy

Abstract

High doses of the angiotensin converting enzyme inhibitor, captopril, is known to cause significant increases in urinary protein excretion in patients with idiopathic membranous nephropathy. To find whether other angiotensin converting enzyme inhibitors yield similar results, we prospectively examined the effect of enalapril in five consecutive patients with idiopathic membranous nephropathy, elevated arterial pressure, and proteinuria and compared them to age-matched controls receiving clonidine. Glomerular filtration rate, 24-hour urinary protein excretion, and arterial pressure were measured. All patients served as their own controls. Those who received enalapril demonstrated an initial increase in proteinuria (-0.3 +/- 0.7 delta gm/day, clonidine vs 3.9 +/- 0.9 delta gm/day, enalapril: P less than .05) despite similar decreases in arterial pressure (-18 +/- 6 delta mm Hg, clonidine vs -22 +/- 6 delta mm Hg, enalapril: NS) and glomerular filtration rate (-1.1 +/- 0.8 delta mL/min, clonidine vs -1.9 +/- 1.2 delta mL/min, enalapril: NS) when compared to the clonidine group. This increase in proteinuria, however, did not occur when these patients were rechallenged with enalapril. To our knowledge, this is the first report to document a significant increase in preexisting nephrotic range proteinuria following administration of nonsulfhydryl ACE inhibitor. This increase, however, appears to be unique to the initial treatment phase of the disease and does not affect long-term management.