Diuretics

The diuretics are a group of drugs that increase the flow of urine. Certain diuretic drugs achieve this by different actions. Those that increase glomerular filtration are called plasma expanders and xanthines. Agents that inhibit the reabsorption of sodium and chloride by direct action on kidney tubules, include mercurials, benzothiazides (hydrochlorothiazide), carbonic anhydrase inhibitors, furosemide and ethacrynic acid. Those that inhibit reabsorption by an indirect method are osmotic diuretics and those that inhibit aldosterone.

It is important to know the cause of edema in determining which drug to use, since only those agents which cause excretion of electrolytes will relieve edema.
Poor results of diuretic therapy can be seen when there is reduced glomerular filtration rate such as is seen in renal insufficiency, and when there is to much reabsorption of sodium and water caused by nephrosis. It can also be seen in heart failure when there is reduced renal blood flow or impaired venous drainage which traps fluid in tissues.

Side effects to diuretic therapy include hypokalemia (low potassium), hyponatremia (low sodium), and transient changes in plasma volume, and renal function.

In order for diuretics to be effective there must be kidney function.