Intracellular Cations and Diuretic Therapy Following Acute Myocardial Infarction

\s=b\In a controlled, prospective, randomized study of the effects of diuretic therapy on serum, lymphocyte, and erythrocyte potassium, magnesium, and calcium concentrations, 155 patients were followed up for six months after experiencing acute myocardial infarction. Of these, 48 patients received furosemide and potassium; 37 patients received hydrochlorothiazide and amiloride hydrochloride; and 70 patients did not require diuretics. Lymphocyte and erythrocyte cation concentrations were all statistically significantly lower in the furosemide-treated patients when compared with the patients in the nondiuretic-therapy group or the hydrochlorothiazide\x=req-\ amiloride-treated group, with no change in serum levels. Since the combination of low intracellular potassium and magnesium concentrations in patients with recent myocardial infarction may be of importance in the cause of arrhythmias, we suggest that potassium- (and magnesium-) sparing diuretics be used in the treatment of patients, when necessary, unless their diuretic needs cannot be met by such agents. (Arch Intern Med 1986;146:1301-1303) T^hiazide and loop diuretics have been shown to induce urinary losses of magnesium,13 whereas potassium-re¬ taining diuretics probably do not have this effect.4 However, the degree of magnesium deficiency is rarely severe enough to cause symptoms: serum magnesium levels may be normal and therefore would not reflect intracellular levels.3S·6 It has been shown that patients receiving prolonged diuretic therapy for congestive heart failure have low magnesium concentrations in their skeletal muscle.78 Since this tech¬ nique is invasive and there is evidence that lymphocyte concentrations of potassium and magnesium may accu¬ rately reflect skeletal and cardiac muscle concentrations,910 we decided to study serum, lymphocyte, and erythrocyte potassium, magnesium, and calcium concentrations in pa¬ tients after they have had an acute myocardial infarction (AMI). We compared the effects of furosemide plus potas¬ sium chloride (Slow K, Ciba-Geigy, Summit, NJ) with the combination of 50 mg of hydrochlorothiazide and 5 mg of amiloride hydrochloride (Moduretic, Merck Sharp & Dohme, Rahway, NJ) on these cation concentrations.