Effect of diuretics on urine magnesium excretion in Asian chronic kidney disease patients

Introduction

Magnesium (Mg) homeostasis is influenced by many factors. Serum Mg and Fractional Excretion of Magnesium (FEMg) increase with chronic kidney disease (CKD), while 24-hour urine magnesium (24UMg) excretion decreases. We hypothesize that serum and urine magnesium is affected differently by the types of diuretics.  We studied the effect of loop and thiazide diuretics on urine and serum magnesium in a group of multi-ethnic Asian CKD patients.

Method

The study population consisted of 227 patients with CKD. Following a 24-hr urine collection, participants underwent glomerular filtration rate (GFR; mL/min/1.73m²) measurement using Tc^99mDTPA and provided a spot urine and blood samples. No patients were on Mg supplementation. Data were analyzed with SPSS V23.

Results

Of the 227 patients with CKD, 72 (31.7%) had GFR>60, 96 (42.3%) had GFR 30-60, and 61 (26.0%) had GFR <30. 44 (19.4%) patients were on loop diuretics, 67 (29.5%) were on thiazide diuretics, and 116 (51.1%) were not on diuretics.

There is no correlation between GFR and serum Mg in any of the patient groups. FEMg is negatively correlated with GFR, for patients not on diuretics (R = -0.517, p<0.001), on loop diuretics (R = -0.397, p = 0.008), and on thiazide diuretics (R = -0.472, p<0.001). 24UMg was only positively correlated in patients without diuretics (R= 0.198 p=0.033) and patients on loop diuretics (R= 0.340, p=0.022) but not in patients on thiazide diuretics.

Conclusions:

FEMg increases with declining GFR, and this effect is not significantly changed with diuretic use. With decreasing GFR, thiazide diuretics are associated with lower total 24UMg compared to loop diuretics.