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Chapter 51
Diuretic Agents
Classes of Diuretics
• Thiazide and thiazide-like diuretics
• Loop diuretics
• Carbonic anhydrase inhibitors
• Potassium-sparing diuretics
• Osmotic diuretics
Function of Diuretic Agents
• Increase the amount of urine produced by the kidneys
• Increase sodium excretion
Indications for Diuretic Use
• Edema associated with congestive heart failure
• Acute pulmonary edema
• Liver disease (including cirrhosis)
• Renal disease
• Hypertension
• Conditions that cause hyperkalemia
Causes of Edema and Ascites in Patients
With Liver Failure
• Reduced plasma protein production
– Results in less oncotic pull in the vascular system and
fluid loss at the capillary level
• Obstructed blood flow through the portal system
– Caused by increased pressure from congested
hepatic vessels
Thiazide and Thiazide-Like Diuretics
• Hydrochlorothiazide (HydroDIURIL)
• Chlorothiazide (Diuril)
• Bendroflumethiazide (Naturetin)
• Benzthiazide (Exna)
• Hydroflumethiazide (Diucardin)
• Methyclothiazide (Aquatensen)
• Polythiazide (Renese)
• Trichlormethiazide (Diurese)
Sites of Action of Diuretics in the Nephron
Indications for Thiazide and Thiazide-Like
Diuretics
• Treatment of edema associated with CHF, liver, or renal
disease
• Monotherapy or adjuncts for the treatment of
hypertension
Focus on the Prototype Thiazide Diuretic:
Hydrochlorothiazide
• Indications: Adjunctive therapy for edema associated
with CHG, cirrhosis, corticosteroid and estrogen therapy,
and renal dysfunction; treatment of hypertension
• Actions: Inhibits reabsorption of sodium and chloride in
distal renal tubules, increasing the excretion of sodium,
chloride, and water by the kidneys
• Oral route: Onset 2 h; peak 4–6 h; duration 6–12 h
• T½: 5.6–14 h; metabolized in the liver and excreted in
urine
Loop Diuretics Currently Available
• Furosemide (Lasix)
– Most commonly used; less powerful than new drugs;
larger margin of safety for home use
• Bumetanide (Bumex) and torsemide (Demadex)
– New drugs; more powerful than Lasix
• Ethacrynic acid (Edecrin)
– First loop diuretic introduced, used less frequently in
the clinical setting
Indications for Loop Diuretics
• Acute CHF
• Acute pulmonary edema
• Edema associated with CHF
• Edema associated with renal or liver disease
• Hypertension
Focus on the Loop Diuretic Prototype:
Furosemide
• Indications: Treatment of edema associated with CHF,
acute pulmonary edema, hypertension
• Actions: Inhibits reabsorption of sodium and chloride
from the proximal and distal renal tubules and the loop of
Henle, leading to a sodium-rich diuresis
• Oral route: Onset 60 min; peak 60–120 min; duration
6–8 h
• IV, IM route: Onset 5 min; peak 30 min; duration 2 h
• T½: 120 min; metabolized in the liver and excreted in
urine
Focus on the Carbonic Anhydrase
Inhibitors Prototype: Acetazolamide
(Diamox)
• Indications: Treatment of glaucoma; edema caused by
CHF, drug-induced edema; centrencephalic epilepsy;
prophylaxis and treatment of acute altitude sickness
• Actions: Inhibits carbonic anhydrase, which decreases
aqueous humor formation in the eye; intraocular
pressure and hydrogen secretion by the renal tubules
• Routes: Oral, SR, IV
• T½: 5–6 hr; excreted unchanged in urine
Potassium-Sparing Diuretics
• Types
– Amiloride (Midamor)
– Spironolactone (Aldactone)
– Triamterene (Dyrenium)
• Uses
– Patients at high risk for hypokalemia associated with
diuretic use
Osmotic Diuretics
• Types
– Glycerin (Osmoglyn), Isosorbide (Ismotic), Mannitol
(Osmitrol), and Urea (Ureaphil)
• Action
– Pull water into the renal tubule without sodium loss
• Indications
– Increased cranial pressure or acute renal failure due
to shock, drug overdose, or trauma