Diuretic Drugs

By selectively regulating solute or fluid reabsorption, the kidneys play the major role in maintaining the volume and composition of extracellular fluid. Many diseases, including congestive heart failure, hepatic cirrhosis, and Cushing’s syndrome (glucocorticoid excess), are associated with or cause significant alterations in extracellular fluid balance. Diuretics inhibit renal sodium transport and thereby interfere with the normal regulatory activity of the kidney. In some instances, administration of a diuretic drug is the primary treatment indicated, while in others it is one of several drugs that are used as part of a treatment regimen. In either case, an ideal diuretic would be one that caused the excretion of “extra” urine with an electrolyte composition similar to that of normal plasma. No such diuretic exists. Thus, although diuretic therapy provides welcome relief from pulmonary congestion, ascites, edema, and hypertension, it also invites complications of organ hypoperfusion that may be accompanied by marked distortions of plasma composition. This chapter includes an overview of the features of fluid balance and renal function that are essential to understanding diuretic action, a discussion of the uses of diuretics for treating abnormalities of fluid balance, and a detailed description of the various classes of diuretics. The practitioner who is armed with the knowledge of the mechanism of action of diuretic drugs and with appropriate recognition and respect for their potential side effects can use these compounds with a high degree of efficacy and safety. D R U G L I S T Diuretic Drugs