[Magnesium and long-term diuretic therapy].

Thiazides and loop diuretics, facilitate the loss of Mg and K resulting in increased excretion in the urine. Although serum-K and serum-Mg values in patients receiving long-term treatment for hypertension or incompensated heart disease usually are normal, muscle-Mg and muscle-K contents are reduced in around 50% of these patients. Mg deficiency increases K loss and K/Mg deficiencies are frequently observed simultaneously. K repletion is often difficult if the accompanying Mg deficiency is not corrected simultaneously. The K/Mg loss from the muscles is accompanied by reduced concentration of Na,K-pumps. These disturbances may produce muscle symptoms, increased sensitivity to digitalis, inhibition of growth and possibly arrhythmias. Evaluation of the K and Mg status during diuretic treatment should be preferentially based on tissue determinations. The muscle biopsy method is rapid, reliable and may reveal conditions of deficiency. In several cases, oral supplements of Mg have proved to be adequate to restore the normal K/Mg status.