Segmental bioimpedance for measuring amlodipine-induced pedal edema: a placebo-controlled study

Background: The development of antihypertensives requires efficient and accurate tools for identifying pedal edema. Methodologies used to gauge the potential of an agent to induce pedal edema in short-term (<4-week) clinical trials have not been reported in the literature.

Objective: The purpose of this study was to identify a robust and practical method for measuring drug-induced pedal edema for use in the clinical development of antihypertensives. The efficacy of segmental bioimpedance in the detection of increased pedal edema was compared with that of clinical pitting assessment, ankle circumference, and water displacement volumetry.

Methods: The study population consisted of male and female healthy subjects and patients with stage 1 or 2 hypertension who were otherwise healthy. Participants were randomly assigned to receive amlodipine 10 mg or placebo once daily in this 6-week, double-blind, parallel-group study. Amlodipine was used as a means of inducing ankle edema, and not for the treatment of hypertension. Patients with hypertension were required to undergo a washout of antihypertensive therapies. Edema was evaluated using segmental bioimpedance at 10 kHz, clinical pitting assessment, ankle circumference, and water displacement at weeks 2, 4, and 6. The ANOVA model used included treatment and baseline values as covariates, with treatment pairs compared via t tests derived from the model.

Results: A total of 47 individuals were randomized (49% male; 29 [62%] with hypertension; mean [SD] age, 59 [5.9] years; baseline body mass index, 28.6 kg/m(2) [2.8]; blood pressure 146.6 [10.7]/93.5 [6.5] and 139.3 [8.3]/89.5 [4.5] in individuals with and without hypertension, respectively; amlodipine 10 mg, n = 24; placebo, n = 23). At weeks 2, 4, and 6, statistically significant treatment differences in changes from baseline were detected using water displacement (mean [90% CI] treatment differences, +39.0 g [+17.9 to +60.1], +61.9 g [+36.1 to +87.6], and +72.2 g [+42.3 to +102.1], respectively; all, P ≤ 0.001), ankle circumference (+4.74 mm [+2.38 to +7.11; P < 0.001], +2.92 mm [+0.33 to +5.49; P = 0.032], and +5.16 mm [+2.21 to +8.11; P = 0.002]), and bioimpedance (-11.7 Ω [-18.1 to -5.4], -18.3 Ω [-26.2 to -10.4], and -20.9 Ω [-29.7 to -12.0]; all, P≤0.001), but no significant differences were detected using clinical assessment of pitting.

Conclusion: In this population of healthy subjects and patients with hypertension, segmental bioimpedance was comparable to water displacement and ankle circumference and outperformed clinical assessment of pitting for the detection of ankle edema, supporting the use of segmental bioimpedance as a drug-development tool to objectively quantify amlodipine-induced pedal edema.