Antiproteinuric effect of olmesartan in patients with IgA nephropathy

Background: IgA nephropathy is one of the most common primary glomerulonephritides, and the clinical course of almost 40% of the patients progresses to end-stage renal disease (ESRD) within 20 years. Angiotensin- converting enzyme (ACE) inhibitors and/or angiotensin II receptor blockers (ARBs) induce a marked renoprotective effect in nondiabetic chronic proteinuric nephropathies including IgA nephropathy. However, in Japan, ACE inhibitors and ARBs are not used for normotensive patients. The purpose of the present study was to evaluate the antiproteinuric effect of olmesartan, one of the ARBs, in normotensive patients with IgA nephropathy in Japan. Methods: Olmesartan was given to 25 patients for 16 weeks. The initial dose was 5 mg and was increased stepwise to 10 mg, 20 mg and 40 mg. Results: Final doses were 40 mg (n = 11), 20 mg (n = 5), 10 mg (n = 7) and 5 mg (n = 2). The change in urinary protein to creatinine ratio was -56.2% +/- 22.8% at week 16. Creatinine clearance showed no changes throughout the study period. Blood pressure (systolic/diastolic) was 118.9 +/- 7.0 / 76.8 +/- 7.4 mm Hg in the lead-in period and decreased to 107.0 +/- 10.1/66.3 +/- 7.8 mm Hg at week 16. At the end of treatment with olmesartan, no correlation was observed between changes in the urinary protein to creatinine ratio and mean blood pressure based on investigation of dispersion diagrams. Conclusions: Olmesartan monotherapy showed robust reduction of urinary protein in normotensive IgA nephropathy patients, suggesting that this effect is independent of its blood pressure-lowering properties.