Fifteen studies met inclusion criteria (n=535 patients, range eight to 278, one study did not report the number of patients). Four of the studies were parallel-group randomised controlled trials (RCTs), four were crossover RCTs, two were pilot studies and five were case series. The eight RCTs were rated as low quality (one study, Jadad score of 2), moderate (three studies, score 3 to 4) and high quality (four studies, score 5).
Adding MRBs to ACE-inhibitor and/or ARB therapy showed a significant decrease in proteinuria. The decrease ranged from 15% to 54% overall (44% to 54% in parallel RCTs, 30% to 38% in crossover RCTs and 15% to 54% in non-RCTs).
Overall, 24 of 436 patients (5.5%) on MRB therapy developed clinically significant hyperkalaemia, using serum potassium level greater than 5.5mEq/L (mmol/L) as the cut-off (15 studies). Hyperkalaemia events were significant in only one of the eight RCTs. There was statistically significant decrease in blood pressure (40% of studies) and glomerular filtration rate (25% of studies) with MRB therapy (15 studies).