Diuretic Agents

Diuretic Agents

Abnormalities in fluid volume and electrolyte composition are common and important clinical disorders. Drugs that block spe-cific transport functions of the renal tubules are valuable clinical tools in the treatment of these disorders. Although various agents that increase urine volume (diuretics) have been described since antiquity, it was not until 1937 that carbonic anhydrase inhibitors were first described and not until 1957 that a much more useful and powerful diuretic agent (chlorothiazide) became available.

Technically, a “diuretic” is an agent that increases urine vol-ume, whereas a “natriuretic” causes an increase in renal sodium excretion and an “aquaretic” increases excretion of solute-free water. Because natriuretics almost always also increase water excre-tion, they are usually called diuretics. Osmotic diuretics and antidiuretic hormone antagonists (see Agents That Alter Water Excretion) are aquaretics that are not directly natriuretic.

 CASE STUDY

A 65-year-old man comes to the emergency department with severe shortness of breath. His wife reports that he has long known that he is hypertensive but never had symptoms, so he refused to take antihypertensive medications. During the last month, he has noted increasing ankle edema, reduced exercise tolerance, and difficulty sleeping lying down, but he reports no episodes of chest pain or discomfort. He now has pitting edema to the knees and is acutely uncomfortable lying down. Vital signs include blood pressure 190/140 mm Hg, pulse 120 bpm, and respiratory rate 20/min. Chest aus-cultation reveals loud rhonchi, but an electrocardiogram is negative except for evidence of left ventricular hypertrophy. He is given a diuretic intravenously and admitted to intensive care. What diuretic would be most appropriate for this man’s case of acute pulmonary edema associated with heart failure? What are the possible toxicities of this therapy