Cardiovascular Drugs Our Patients Take
Course Number: 581
Course Contents
Drugs that Regulate Extracellular Fluid Volume
About ⅔ of total body water is intracellular and ⅓ is extracellular. Nearly ¾ of the extracellular fluid (ECF) resides in the interstitial space. The remaining ¼ of the ECF, a determinant of tissue perfusion, i.e., the distribution of O2 and nutrients, is in plasma. Depletion of plasma volume (1) activates the renin-angiotensin-aldosterone system (RAAS), (2) promotes antidiuretic hormone release, and (3) increases renal sympathetic activity; volume overload promotes the release of natriuretic peptides.4
Excessive Na+ and H2O retention, primarily a result of renal abnormalities, is responsible for volume-based hypertension.4 Pathological Na+ and H2O retention can also lead to transudative edema associated with heart failure, cirrhosis of the liver, and nephrotic syndrome4 Drugs in the top 300 that regulate extracellular fluid volume (Table 2) can be divided into two broad classes: (1) agents that act directly on the nephron to increase renal Na+ excretion and (2) drugs that modulate the RAAS.2,4,10.
Table 2. Drugs that Regulate Volume.2,4,10
| Drugs | Mechanisms of Action | Common Indications |
|---|---|---|
Thiazide diuretics
| Inhibit Na+ reabsorption by cells of the distal convoluted tubule | Hypertension Adjuncts in chronic edema states associated with
|
Loop diuretics
| Inhibit Na+ reabsorption by cells of the Loop of Henle | |
Collecting duct (potassium-sparing) diuretics
| Spironolactone inhibits Na+ reabsorption by inhibiting aldosterone action Triamterene inhibits Na+ reabsorption by principal cells of the collecting duct | |
Angiotensin converting enzyme (ACE) inhibitors
| Inhibit the conversion of angiotensin (AT) I to AT II thereby decreasing
| Hypertension Adjuncts in the prevention and treatment of
|
Angiotensin II receptor antagonists
| Antagonize the action of AT II at AT1 receptors May indirectly increase AT2-receptor-related vasodilation |