Thiazide diuretics hypomagnesemia with

Many drugs can cause hypokalemia (Table 78-5) and it is most commonly seen with use of loop and thiazide diuretics. Other causes of hypokalemia include diarrhea, vomiting, and hypomagnesemia. 

Therapy with hydrochlorothiazide, up to 50 mg twice daily, or chlorthalidone, 50-100 mg daily, is recommended. Loop diuretics such as furosemide and ethacrynic acid should not be used because they increase urinary calcium excretion. The major toxicity of thiazide diuretics, besides hypokalemia, hypomagnesemia, and hyperglycemia, is hypercalcemia. This is seldom more than a biochemical observation unless the patient has a disease such as hyperparathyroidism in which bone turnover is accelerated. Accordingly, one should screen patients for such disorders before starting thiazide therapy and monitor serum and urine calcium when therapy has begun. 

Hypomagnesemia is common with both loop and thiazide diuretics. In 242 patients the frequency was 19% (10). It was corrected with potassium magnesium citrate, whereas potassium citrate or potassium chloride alone had little corrective effect. 

Decreased magnesium levels, that is, levels of 1.2 mEq/L (0.64 mmol/L) or less, may be noted in patients with conditions that cause excessive urinary loss of magnesium, including poorly controlled diabetes and alcohol abuse, or in patients using drugs such as loop and thiazide diuretics (e.g., Lasix, Bumex, Edecrin, and hydrochlorothiazide), cisplatin (which is used widely to treat cancer), and the antibiotics gentamicin, amphotericin, and cyclosporine. Hypomagnesemia also can... 

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