Magnesium deficiency: pathogenesis, prevalence, and clinical implications.

Hypomagnesemia is probably the most underdiagnosed electrolyte deficiency in current medical practice. Patients with cardiovascular disease who are at greatest risk for the development of magnesium deficiency are those treated with diuretics or digitalis. Both potassium and magnesium deficiencies are associated with increased ventricular ectopy and may increase the risk of sudden unexpected death. Refractory potassium repletion can be caused by concomitant magnesium depletion, and can be corrected with magnesium supplementation. Routine serum magnesium determination is recommended whenever the testing of electrolyte levels is required, especially in patients taking diuretic drugs or digitalis. Because hypomagnesemia is not necessarily present in a magnesium-deficient state, it is recommended that both potassium and magnesium be repleted in patients with hypokalemia. Potassium-/magnesium-sparing diuretics may be helpful in the prevention of these electrolyte deficiencies.