DIURETIC AND ANTIDIURETIC AGENTS
Section I. DIURETIC AGENTS
In Lesson 3 of this subcourse, congestive heart failure was described as a
condition characterized by sodium retention that results in expanded extracellular fluid
volume or edema. This same process of increased tubular reabsorption of sodium-
resulting in an accumulation of fluid--may accompany cirrhosis of the liver, renal
disease, toxemia of pregnancy, the side effects of drugs, and other states of fluid
retention. In all of these conditions, treatment of sodium retention is what is desired.
REMEMBER: WHERE SODIUM GOES, WATER GOES! Therefore, the treatment as
sodium retention by sodium excretion--not just the increase in urine volume--is the
desired goal. Diuretic agents increase the amount of sodium excreted from the body.
8-2. DEFINTION OF DIURETIC
A diuretic is any agent that produces diuresis (an increase in the volume of urine
output that results in the mobilization of edema fluid). You have heard the term edema
before. Edema is the presence of abnormally large amounts of fluid in the body. Many
diuretics reduce edema by increasing the amount of sodium removed from the body.
Remember, where sodium goes, water goes. Thus, when sodium is removed from the
body, there is a corresponding increase in the volume of urine produced.
8-3. USES OF DIURETICS
The general uses of diuretics include the treatment of congestive heart failure,
hypertension, glaucoma, ascites, toxemia of pregnancy, and diabetes insipidus.
Congestive heart failure has been discussed in Lesson 3 of this subcourse,
hypertension has been discussed in Lesson 7 of this subcourse, and glaucoma has
been discussed in MD0805, Pharmacology II. Review these materials if you have a
need. The other conditions will be explained in this paragraph. Ascites is the
accumulation of fluid in the abdominal cavity. Toxemia of pregnancy is a group of
pathologic conditions--essentially metabolic disturbances--which sometimes occurs in
pregnant women. Toxemia of pregnancy is manifested by preeclampsia (a toxemia of
late pregnancy characterized by hypertension, albuminuria, and edema) and fully
developed eclampsia (this condition includes convulsions and coma, which might occur
in a pregnant woman or in a woman who has just delivered). Hypertension, edema,
and/or proteinuria characterize eclampsia. Diabetes insipidus is a metabolic disorder
caused by a lack of production of antidiuretic hormone (ADH), which is marked by great
thirst and the passage of a large amount of dilute urine with no excess of sugar.