Nifedipine and extracellular water in dialysis arterial hypertension

Nifedipine is a Ca-antagonist drug that reduces contractility of vascular smooth muscle, and is used in the treatment of arterial hypertension and of stable and vasospastic angina. Aim of this study is to evaluate long-term effect of nifedipine on distribution of body fluid compartment, assessed by BIA (Bio-Impedance Analysis), and on cardiac function, in hypertensive patients on dialysis. Two groups of hypertensive patients were compared: a) a first group of nine patients (5 Male, 4 Female; age 62.67 +/- 10.39) treated with nifedipine (30 mg/day) for one year; b) a control group of sixteen dialysis patients (9 Male, 7 Female; age 56.31 +/- 14.44), previously hypertensive, with normal blood pressure without anti-hypertensive drugs for three months or more. By BIA, extracellular water percentage (ECW%) is higher in nifedipine-treated patients (p < 0.001) in comparison with the control group before dialysis; no other difference is present. The intradialytical variations (before dialysis vs. the end of dialysis) of body fluid compartments are a significant decrease of total body water % (52.33 +/- 2.89 vs. 48.72 +/- 3.35, p < 0.001), ECW% (40.97 +/- 2.2 vs. 37.56 +/- 3.47, p < 0.005), Left Ventricular End-Diastolic Volume (81.1 +/- 14.6 vs. 63.4 +/- 21.66 ml/m2, p < 0.003), Cardiac Output (3.35 +/- 0.71 vs. 2.51 +/- 0.76 l/min/m2, p < 0.04) and Stroke Volume (45.76 +/- 10.21 vs. 34.34 +/- 9.98 ml/m2, p < 0.02) in nifedipine-treated patients. Our findings suggest that nifedipine induces intermittent and prolonged expansion of extra-cellular volume. This condition, in patients otherwise without clinical and echocardiographic signs of heart failure, can be potentially detrimental for cardiac function on long-term nifedipine treatment.