en تخصصي Special پژوهشي Research Abstract Objectives: Interruption of rennin-angiotensin-aldosterone system has become a leading therapeutic strategy in the treatment of diabetic nephropathy however, ACEIs and ARBs do not uniformly suppress the rennin-angiotensin-aldosterone system. Plasma aldosterone levels are elevated in a group of patients despite therapy and this phenomenon known as aldosterone escape or aldosterone break through. Materials and Methods: Forty-two type 2 diabetic patients with overt proteinuria were randomized into two groups and according to double-blind case-control study, one group was treated with spironolactone and others were treated with placebo for 4 months. Twenty-four hours urine protein, glomerular filtration rate (GFR) and blood pressure were measured at baseline and after 4 months of treatment. Serum potassium was checked at baseline and one month of treatment. Results: Urine protein decreased in case group by 26.5% at the end of 4 months, but increased in control group by 17.9% (P=0.003). GFR did not have any significant change in case group (P<0.354), but decreased in case group significantly (P<0.001). Conclusion: Our study showed that spironolactone 12.5 mg/day is safe (without hyperkalemia and gynecomastia) and effective to decrease proteinuria in diabetic patient with CKD1-2. Diabetic nephropathy, Aldosterone, Spironolactone, Aldosterone escape, Chronic kidney disease. 144 150 http://ijdo.ssu.ac.ir/browse.php?a_code=A-10-30-60&slc_lang=en&sid=1 Farzaneh Najafi No Assistant Professor Division of Nephrology, Yazd Diabetes Research Center, Yazd. Iran Bibi Saideh Rezvaninejad Yes Resident of internal medicine, Division of Nephrology, Department of Internal Medicine, Shaheed Sadoughi University of Medical Sciences and Health Services, Yazd, Iran. Seyed Mohammad Mohammadi No Assistant Professor of Endocrinology, Yazd Diabetes Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran