Twelve trials (4,104 participants, range 20 to 1,204) were included. The median quality score was 5 (range 2 to 6).
Blood pressure reduction and response rate: The trandolapril/verapamil combination reduced systolic blood pressure (WMD 6.14, 95% CI 3.59 to 8.70) and diastolic blood pressure (WMD 2.49, 95% CI 0.81 to 4.17) more than verapamil alone, based on seven studies. Significant heterogeneity for the diastolic blood pressure analysis (p=0.001, Ι²=68%) was no longer seen when one small poor-quality trial was removed from the analysis. The trandolapril/verapamil combination reduced diastolic blood pressure more than trandolapril alone (WMD 3.71, 95% CI 1.84 to 5.57; nine studies) but not systolic blood pressure. No significant differences were found for blood pressure response rate, based on an analysis of four studies.
24 hour proteinuria and albuminuria: The trandolapril/verapamil combination reduced 24-hour proteinuria (WMD 0.84, 95% CI 0.22 to 1.45; two studies) and albuminuria (WMD 255, 95% CI 119.26 to 390.74; two studies) more than verapamil alone. It also reduced albuminuria more than trandolapril alone (WMD 136.77, 95% CI 12.44, 261.09; two studies).
Adverse events: Overall incidence of adverse events was comparable between treatment groups. No significant differences were found for incidences of cough and constipation.