Cyclosporine enhances salt sensitivity of body water composition as assessed by impedance among psoriatic patients with normal renal function.

Objective: Cyclosporine (CsA) therapy may be accompanied by a significant increase in blood pressure, either sodium (Na+) independent or Na+ dependent. The relationship between Na+ intake and body water distribution among patients treated with CsA has not been evaluated. We report the study, by bioelectrical impedance analysis (BIA), of water composition changes after dietary salt manipulations both before and during CsA treatment of psoriatic patients.

Methods: Ten normotensive psoriatic patients, ages 37 +/- 12 years (range, 19 to 54), with normal renal function were included. Each patient was assessed by BIA in 2 phases, before (phase 1) and during (phase 2) CsA therapy (3 mg/kg/day). In both phases, each patient was assessed in basal conditions (basal1 and basal2), on day 7 of a low-sodium diet (LS1 and LS2; 20 mEq/day) and on day 7 of a high-sodium diet (HS1 and HS2; 350 mEq/day). Plasma creatinine (Pcr), urinary volume excretion (Uv), urinary sodium (UNa+), urinary potassium (UK+), urinary osmolality (UOsmo), weight (Wt), resistance (R), reactance (Xc), total body water (TBW), extracellular water (ECW), intracellular water (ICW), Na:K exchangeable (Nae:Ke), phase angle (PA), and body cell mass (BCM) were evaluated. Blood pressure was monitored during 24 hours on the last day of each diet. Paired Student's t-test was used to analyze the different phases.

Results: Before CsA treatment, Wt, TBW and Nae:Ke were lower during LS1 than during basal1, whereas TBW was higher during HS1 than during LS1. During CsA, Wt, TBW, ECW, and Nae:Ke were lower during LS2 than during basal2, whereas ICW and PA were higher during LS2 than during basal2. HS2 showed higher TBW, ECW, and Nae:Ke and lower ICW, PA, and BCM than during LS2. Systolic blood pressure was higher during HS2 than during LS2 or HS1. In addition, diastolic blood pressure was higher during HS2 than during HS1.

Conclusion: Body hydration status was more sensitive to dietary salt fluctuations during CsA treatment than without CsA, and a high-sodium diet seemed to enhance the CsA-induced hypertension side effect. Moreover, patients on low sodium intake under CsA treatment displayed neither any disturbance of body water composition nor any blood pressure change. Our data suggest that a low sodium intake might be very useful in preventing undesirable pressure and volume changes brought about by CsA treatment.