Diuretics

Question 1

Explain the main function of diuretics

Answer 1

They increase the kidney’s output of urine

Goal: lower BP and/or decrease edema

Question 2

List the first 2 types of diuretics & their sites of action in the nephron

Answer 2

1. Carbonic anhydrase inhibitors
   Site: PCT (65-70% Na is absorbed)
2. Loop diuretic
   Site: TAL or thick ascending limb of nephron loop (25% Na is absorbed)

Question 3

List the next 2 types of diuretics & their sites of action in the nephron

Answer 3

3. Thiazides
   Site: DCT (5% Na is absorbed)
4. K-sparing diuretics
   Site: collecting duct (1-5% Na is absorbed)

Question 4

Recall which of the 4 diuretics is the most potent

Answer 4

loop diuretic (because it acts on TAL)

Question 5

Explain the MOA of loop diuretics

Answer 5

Blocks reabsorption of Na, Cl, and K in TAL of nephron loop

Question 6

Name a commonly used loop diuretic

Answer 6

Furosemide (Lasix)

Question 7

Indications for loop diuretics

Answer 7

Used when critical fluid removal is necessary

• pulmonary edema
• renal failure (loop diuretic is effective even with low GFR!!)
• CHF

Question 8

Name an adverse side effect to monitor closely when using loop diuretics

Answer 8

dehydration

Question 9

List signs and symptoms of dehydration

Answer 9

• dry mouth
• excessive thirst
• oliguria (small amount of urine)
• dark urine

Question 10

What is the medical consequences of dehydration

Answer 10

Severe dehydration can lead to hypovolemia and shock.

This also puts the patient at risk to develop clots.

Question 11

Recall which electrolytes may be depleted with the use of loop diuretics

Answer 11

Potassium

***Digoxin + Furosemide has a potential problem! Lasix can cause hypokalemia, which puts patients at risk of digoxin toxicity –> monitor K level closely!

Question 12

Describe a strategy to reduce the risk of ototoxicity with intravenous (IV) administration of loop diuretics

Answer 12

Do IV push very slowly!

Question 13

What are other (minor) adverse effects of loop diuretics

Answer 13

Hyperglycemia
Hyperuricemia
High LDL level
Low Mg (muscle weakness, tremors, dysrhythmias)
Low Ca (teatny)

Question 14

List 3 other examples of loop diuretics

Answer 14

Bumetanide
Torsemide
Ethacrynic acid

Question 15

Thiazide diuretics: similarities to loop diuretics

Answer 15

Increase the renal excretion of Na, Cl, K, and water

Also elevate plasma glucose & uric acid

Question 16

Thiazide diuretics: differences from loop diuretics

Answer 16

Thiazides are not effective when GFR is low

Question 17

Identify the most commonly prescribed thiazide medication

Answer 17

Hydrochlorothiazide (Microzide)

Question 18

Advise a patient on the best time of day to take a thiazide medication

Answer 18

Take it in the morning!

Thiazide increase urine output 2 hours after oral dose & lasts up to 12 hours.

Question 19

List potential side effects of thiazides

Answer 19

Same as loop diuretics except for ototoxicity

electrolyte imbalances
dehydration/hypotension
Elevated glu, uric acid, and cholesterol

Question 20

2 drugs interactions that you should be careful when administering thiazide

Answer 20

Same as loop diuretics
- digoxin toxicity
- lithium toxicity

Question 21

Describe the function of K-sparing diuretics and how they are prescribed

Answer 21

K-sparing diuretics cause the mildest increase in urine output

Not often used in monotherapy, used with loop diuretics to counteract K loss

Question 22

Name the 2 types of potassium-sparing diuretics

Answer 22

1. Aldosterone antagonists: spironolactone (decrease serum Na, increase serum K)
2. Non-aldosterone antagonists: triamterene & amiloride

Question 23

Explain how mannitol increases urine output

Answer 23

Mannitol does not get reabsorbed and stay in nephron –> creates osmotic pressure and causes increased water diuresis

Question 24

Recall the route of mannitol administration

Answer 24

IV

Question 25

List the indications for mannitol use

Answer 25

1. increased intracranial pressure (ICP)
2. Elevated intraocular pressure
3. low output acute renal failure

Question 26

Describe the potential side effects of mannitol

Answer 26

Mannitol causes fluid to move from inside the cells into the intravascular space
–> be careful with patients with CHF and pulmonary edema (they are already fluid overload)