We appreciate the interesting information and comments provided by Dr Gardner and her colleagues. Overall, they observed 23% of their patients receiving digoxin therapy to have electrolyte disturbances (hyponatremia, 8%; hypokalemia, 11%; and hypomagnesemia, 4%), half of our reported incidence of 56%.1 Since 15% of the overall variance between the two reports can be accounted for by the differences in hypomagnesemia (their 4% vs our 19%), the question arises as to whether this variance could account for reported differences. It would appear that the answer is affirmative. For example, the overall electrolyte imbalance in Dr Gardner's series (23%) contrasted with our 56% would be considerably narrowed to 38% (23% +15% magnesium difference) compared with our 56%. Hyponatremia and hypomagnesemia appear to be linked and parallel the relationship between hypokalemia and hyponatremia.2 Dyckner et al have reported hyponatremia and hypomagnesemia with correction of hyponatremia taking place with magnesium
Whang R. Hypomagnesemia in Digitalized Patients-Reply. Arch Intern Med. 1986;146(3):607–608. doi:10.1001/archinte.1986.00360150260041
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