aminophylline infusion induced excretion of magnesium during magnesium loading test in critically ill patients

the aim of this study was to investigate the prevalence of mg deficiency and effect of aminophylline infusion on urine magnesium concentration after magnesium loading test (mlt). to determine serum mg, venous blood specimens were obtained just before the first mlt. two mlts were performed. the first one was done before starting aminophylline infusion and the 2nd one was done during aminophylline infusion. urine samples were collected from the starting of mg infusion in each phase. although low serum mg was present only in 2 patients, mlt showed mg deficiency in 18 patients. mlt detected mg deficiency in 13 out of 14 patients with normal serum mg, in 2 out of 2 subjects with serum hypomagnesemia, and in 3 out of 5 cases with serum hypomagnesemia. there was no relationship between mg retention, age and serum mg concentrations. aminophylline administration increased the 24-h urine mg concentration by 29.3%.