OBJECTIVE - Irbesartan is renoprotective in patients with type 2 diabetes and microalbuminuria. Whether the observed reduction in microalbuminuria is reversible (hemodynamic) or persistent (glomerular structural/biochemical normalization) after prolonged anti hypertensive treatment is unknown. Therefore, the present substudy of the Irbesartan in Patients with Type 2 Diabetes and Microalbuminuria Study (IRMA-2) investigated the reversibility of kidney function changes after withdrawal of 2 years' antihypertensive treatment. RESEARCH DESIGN AND METHODS - The substudy included 1.33 hypertensive type 2 diabetic patients with persistent microalbuminuria in IRMA-2, randomized to double-masked treatment with either placebo, irbesartan 150 mg, or irbesartan 300 mg o.d. for 2 years. Arterial blood pressure, overnight urinary albumin excretion rate, and glomerular filtration rate (GFR) were determined repeatedly. RESULTS - Baseline characteristics were similar in the placebo, irbesartan 150-mg, and irbesartan 300-mg groups. At the end of the study, mean arterial blood pressure (MABP) was similarly lowered to 105 +/- 2 (mean +/- SE), 103 +/- 2, and 102 +/- 2 mmHg, respectively (P < 0.05 Versus baseline), and urinary albumin excretion rate reduced by 8% (- 16 to 27) (NS), 34% (95% CI 8-53), and 60% (46-70) (P < 0.05). Rates of decline in GFR were L3 - +/- 0.7, 1.2 +/- 0.7, and 1.0 +/- 0.8 ml. min(-1) .1.73 m(-2) per month, respectively, during the initial 3 months of the study and 0.3 +/- 0.1, 0.3 +/- 0. 1, and 0.4 +/- 0.1 ml . min(-1) . 1.73 m(-2) per month in the remaining study period. One month after Withdrawal of all antihypertensive medication, MABP remained unchanged in the placebo group, 105 +/- 2 mmHg, but increased significantly in the ' irbesartan groups, to 109 +/- 2 and 108 +/- 2 mmHg, respectively. Compared With baseline, urinary albumin excretion rate was increased by 14% (-17 to 54) in the placebo group and by 11% (-26 to 65) in the irbesartan 150-mg group but was persistently reduced by 47% (24-73) in the irbesartan 300-mg group (P < 0.05). GFR levels increased to baseline values in the placebo group and approached initial levels in irbesartan groups. CONCLUSIONS - Persistent reduction of microalbuminuria after withdrawal of all antihypertensive treatment suggest's that high-dose irbesartan treatment confers long-term renoprotective effects.
