[Action of trichlormethiazide and amiloride on cellular Na+, K+ and Mg+ concentrations]

While diuretic-induced changes of plasma electrolyte concentrations have often been described, comparatively few data exist on intracellular electrolyte concentrations under diuretic treatment. Therefore, we studied the effect on intracellular Mg2+, Na+ and K+ concentrations of a thiazide diuretic (trichlormethiazide 4 mg/d) in red blood cells of 14 patients with mild essential hypertension, and of a combination of a thiazide diuretic and a potassium-sparing diuretic (trichlormethiazide and amiloride 2 mg/d each) in red blood cells of 11 patients with mild essential hypertension. Measurements were performed by atomic absorption spectroscopy and flame photometry before starting treatment and after 4 and 8-12 weeks' diuretic treatment. There was no significant change in intracellular Na+ and K+ concentrations under either form of diuretic treatment. Intracellular Mg2+ concentrations decreased significantly under thiazide therapy, whereas there was a significant increase in intracellular Mg+ concentrations under thiazide and potassium-sparing combined diuretic therapy. The results show that the combination of a thiazide diuretic and a potassium-sparing diuretic is a useful means to avoid intracellular Mg2+ loss.