Leg edema with (S)-amlodipine vs conventional amlodipine given in triple therapy for hypertension: a randomized double blind controlled clinical trial

BACKGROUND Leg edema is a common adverse effect of dihydropyridine Calcium Channel Blockers (CCB) that may need dose reduction or drug withdrawal, adversely affecting the antihypertensive efficacy. Leg edema is reported to occur less often with (S)-amlodipine compared to conventional racemic amlodipine. We aimed to find the incidence of leg edema as a primary outcome and antihypertensive efficacy with (S)-amlodipine compared to conventional amlodipine. METHODS This prospective, double-blind, controlled clinical trial randomized 172 hypertensive patients, not controlled on beta-blockers (BB) and angiotensin converting enzyme inhibitors/angiotensin receptor blockers (ACEI/ARB), to either conventional amlodipine (5-10 mg; n = 86) or (S)-amlodipine (2.5-5 mg; n = 86), while continuing their previous anti-hypertensive medications. Sample was sufficient to find a difference in edema between the interventions with 80 % power at 5 % significance level. Intension to treat analysis (ITT) for safety data and per protocol analysis for efficacy data was performed. Fischer's exact test was applied to observe difference between responder rates and proportions of subjects having peripheral edema in the two groups. Pitting edema test scores were compared using Mann-Whitney test. RESULTS Altogether 146 patients (amlodipine, n = 76 and (S)-amlodipine, n = 70) completed 120 days treatment. Demographic variables and treatment adherence were comparable in the two groups. Incidence of new edema after randomization was 31.40 % in test group and 46.51 % in control group [p = 0.03; absolute risk reduction (ARR) = 15.1 %; Number Needed to Treat (NNT) = 7, ITT analysis]. Pitting edema score and patient rated edema score increased significantly in the control compared to test group (p = 0.038 and 0.036 respectively) after treatment period. Edema scores increased significantly in the control group from baseline (p < 0.0001). Responders in blood pressure were 98.57 % in test and 98.68 % in control group. Most common adverse events (AE) were pitting edema and increased urinary frequency. Incidence of all AEs other than edema was similar in both groups. Two serious AEs occurred unrelated to therapy. Biochemical and ECG parameters in the two groups were comparable. CONCLUSIONS In hypertensive patients not controlled on prior BB and ACEI/ARB therapy, addition of (S)-amlodipine besylate at half the dose of conventional amlodipine provides better tolerability with reduced incidence of peripheral edema, and equal antihypertensive efficacy compared to amlodipine given at usual doses. TRIAL REGISTRATION Sri Lanka Clinical Trials registry: www.slctr.lk, SLCTR/2013/006.