Background: The current belief is that the calcium channel blocker (CCB)-induced edema is due to a preferential arterial over venous dilatation leading to increased fluid filtration. We challenged this conviction by measuring the lymphatic removal of interstitial fluid during chronic systemic treatment with the CCB, amlodipine. Lymphatic vessels could potentially be an off-target effect of the drugs and play a role in CCB edema. Methods and Results: Sixteen healthy postmenopausal women completed a 12-week double-blinded randomized placebo-controlled crossover trial. Lymphatic function was assessed by near-infrared fluorescence imaging. The lymphatic function during amlodipine treatment compared with placebo did not show any difference in pumping pressure (53.9 ± 13.9 mmHg vs. 54.7 ± 9.4 mmHg, p = 0.829), contraction frequency (0.4 ± 0.2/min vs. 0.4 ± 0.3/min, p = 0.932), refill time (440 ± 438 seconds vs. 442 ± 419 seconds, p = 0.990), or propagation velocity of lymph packets (18 ± 10 mm/s vs. 15 ± 7 mm/s, p = 0.124). However, the subjects who developed edema during CCB treatment had a 20% lower baseline lymphatic pumping pressure (48.9 ± 4.4 mmHg, n = 7) than the subjects not affected by treatment (59.1 ± 1.2 mmHg, n = 9, p = 0.025). Contraction frequency, refill time, and lymph packet velocity showed no differences in baseline values between the two groups. Conclusion: Our results suggest that CCB does not directly impair lymphatic function. However, our results show that a reduced lymphatic function predisposes to CCB edema, which may explain why some patients develop edema during treatment.
Keywords: amlodipine; calcium channel blockers; edema; humans; lymphatic dysfunction; near-infrared fluorescence imaging.