Diuretic-Related Side Effects: Development and Treatment

Domenic A. Sica, MD

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Acid-Base Changes

Mild metabolic alkalosis is a common feature of thiazide diuretic therapy, particularly at higher doses. Severe metabolic alkalosis is much less frequent and, when it occurs, it is in association with loop diuretic use. The generation of a metabolic alkalosis with diuretic therapy is primarily due to contraction of the extracellular fluid space caused by urinary losses of a relatively HCO3 -free fluid.[44] Diuretic-induced metabolic alkalosis is best managed by administration of K+ and/or Na+ chloride, although Na+ chloride administration may be impractical in already volume-expanded patients (such as those with CHF). In such cases, a K+-sparing diuretic or a carbonic anhydrase inhibitor, such as acetazolamide, may be considered. Metabolic alkalosis also impairs the natriuretic response to loop diuretics and may play a role in the diuretic resistance occasionally found in the CHF patient.[45] All K+-sparing diuretics can cause hyperkalemic metabolic acidosis, which in elderly patients, or in those with renal impairment or CHF, can reach a life-threatening level.[46]

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