Uresin Y et al compared the efficacy and safety of aliskiren with that of ramipril in patients with diabetes and hypertension. Aliskiren was found to be more effective at lowering systolic blood pressure (SBP) than ramipril, and showed no inferiority in reducing diastolic blood pressure (DBP). When used in combination with ramipril, aliskiren showed a significant additional reduction in both SBP and DBP. In the same study, plasma renin concentration (PRC) was significantly increased with each monotherapy and when combined, PRC increased to a greater level than the sum of the effects of each alone. The reactive rise in PRC was associated with a concomitant rise in plasma renin activity (PRA) in the ramipril group, an effect that was suppressed when combined with aliskiren.