A chronic alcoholic presenting with hypokalemia is likely also hypomagnesemic. In order to achieve effective correction of potassium levels, both potassium and magnesium must be replaced.
Concurrent hypokalemia and hypomagnesemia is commonly seen in chronic alcoholics due to the following proposed mechanism: 1) initial hypomagnesemia develops secondary to malnutrition and decreased renal absorption of magnesium 2) hypomagnesemia then leads to inappropriate kaliuresis and resulting hypokalemia. Magnesium inhibits potassium channel efflux in the kidney; therefore, low levels of magnesium lead to increased potassium wasting. It should be noted that there are likely also additional independent factors that lead to the development of hypokalemia in alcoholics. When hypokalemia is refractory to appropriate potassium supplementation, evaluate hypomagnesemia as a potential cause and replace magnesium as appropriate.
DiPalma discusses hypomagnesemia in relation to alcoholism and co-existent hypokalemia. Inadequate dietary intake of magnesium commonly occurs in alcoholics and is the most frequent cause of the hypomagnesemia that is often seen in these patients. In addition to hypokalemia, hypomagnesemia is also associated with hypocalcemia.
Elisaf et al. conducted a study of 35 patients to determine the clinical and laboratory characteristics of patients with hypomagnesemia, hypokalemia, and hypocalcemia. Cisplatin use and alcoholism were the 2 most common causes of this constellation of electrolyte abnormalities within this cohort. These patients exhibited inappropriate renal calcium and potassium wasting. In addition, other commonly noted acid base abnormalities in these patients included hypophosphatemia, respiratory alkalosis, metabolic alkalosis, and mixed acid-base disorders.
Figure A shows an EKG of a patient with hypokalemia; note the flattened T waves and presence of U waves. Illustration A is a depiction of the electrolyte transport in the thick ascending limb. Magnesium may have a role in inhibiting the ROMK channel, which is responsible for potassium efflux; low levels of magnesium result in less inhibition of potassium efflux, leading to increased potassium loss in the urine.
Answer 1: Potassium replacement alone without correcting likely coexistent hypomagnesemia will make effective potassium replacement difficult.
Answers 3-5: These medications and treatment options are indicated in patients suffering from hyperkalemia, not hypokalemia. Treatment of hyperkalemia includes calcium gluconate for cardiac membrane stabilization, sodium bicarbonate, ß2 adrenergic agonists, insulin/glucose, kayexalate, loop diuretics, and hemodialysis (for severe/intractable hypokalemia or in patients with renal failure).
DiPalma JR. Magnesium replacement therapy. Am Fam Physician. 1990 Jul;42(1):173-6.
PMID:2195859 (Link to Abstract)
Elisaf M, Milionis H, Siamopoulos KC. Hypomagnesemic hypokalemia and hypocalcemia: clinical and laboratory characteristics. Miner Electrolyte Metab. 1997;23(2):105-12.
PMID:9252977 (Link to Abstract)