Diuretics

Question 1

Diuresis

Answer 1

Increased urine flow rate

Question 2

What are the major osmolytes being reabsorbed by the kidney?

Answer 2

Sodium Chloride (NaCl)
Bicarbonate (HCO3-)
Calcium (Ca2+)

Question 3

What are the major osmolytes secreted by the kidney?

Answer 3

Hydrogen (H+)
Potassium (K+)

Question 4

Where is most of the NaCl and water reabsorbed?

Answer 4

Proximal tubule: 65-75%
Loop of Henle (20-25)
Distal nephron (5-7)

Question 5

Indication for diuretic use

Answer 5

-Reduce extracellular fluid volume (pulmonary congestions, ascites, CHF)
-Oliguric renal failure
-Hypertension (Exercise Induced Pulmonary Hemorrhage)
-Promote urinary excretion of selected agents/electrolytes

Question 6

Which class of diuretics is most commonly used?

Answer 6

Loop diuretics

Question 7

Osmotic Diuretics Mechanism

Answer 7

Inhibits water reabsorption in the proximal tubule and loop by increasing the osmotic gradient in the lumen

Question 8

Mannitol

Answer 8

Osmotic Diuretic
-freely filtered at glomerulus
Used to treat oliguric renal failure, cerebral edema, acute glaucoma

Question 9

Carbonic Anhydrase Inhibitors Mechanism

Answer 9

Increase loss of bicarb and tendency to increase urine pH
(b/c bicarb is basic)

Question 10

Acetazolamide

Answer 10

Carbonic Anhydrase inhibitor
Weak diuretic effect
Alkalinizing effect on urine -> systemic acidosis
May cause hypokalemia
Used to treat metabolic alkalosis, glaucoma, altitude sicknes

Question 11

Loop Diuretics

Answer 11

Inhibits NaCl reabsorption in the thick ascending limb of the loop of Henle
-Most effective diuretic
-Most commonly used

Question 12

Furosemide

Answer 12

Lasix, Salix
Loop diuretic
Most effective diuretic and most widely used in vet med
May cause hypokalemia and increase urinary loss of Ca2+
Used to treat oliguric renal failure, CHF, acute pulmonary hypertension, and EIPH

Question 13

Oliguric

Answer 13

Low urine output

Question 14

Effects of furosemide on racehorse performance

Answer 14

Used for Exercise Induced Pulmonary Hemorrhage
-fluid loss = decr. body weight
-reduced BP in pulmonary circulation
-Bronchodilation
-Diuretic effect can mask the presence of other drugs in the urine

Question 15

Thiazide Diuretics Mechanism

Answer 15

Distal convoluted tubule
Prevent resorption of Na and Cl in the distal tubule by blocking the symporter > Na and Cl retained in the filtrate

Question 16

Chlorothiazide

Answer 16

Thiazide diuretic
Used to treat nephrogenic diabetes insipidus, udder edema in cattle, Ca2+ containing uroliths

Question 17

K+ sparing Diuretics

Answer 17

Other diuretics increase Ka+ in distal segments which leads to K+/H+ loss. These help maintain electrolyte balance.
Useful in patients with CHF

Question 18

Spironolactone

Answer 18

K+ sparing diuretic
Block activity of aldosterone
Used in combo w/ a loop diuretic to prevent hypokalemia
-Used to treat hormonal acne in women

Question 19

Amiloride

Answer 19

Epithelial Sodium channel blocker
Used in combo with loop diuretics
K+ sparing diuretic

Question 20

Digoxin and diuretics

Answer 20

Have to be careful b/c diuretics lead to K depletion which in combo with digoxin can increase arrhythmias
(K+ sparing are better)

Question 21

How do the collecting ducts work

Answer 21

Secretion of ADH (vasopressin) opens aquaporins and allows water to flow back into the cell, concentrating the urine
Diabetes insipidus results from lack of ADH > severe diuresis

Question 22

Demeclocycline

Answer 22

Aquaretic: Antagonize ADH receptors in the kidney
Promotes solute free water clearance
Off target effect of antibiotic