Diuretics and Aquaretics Flashcards
1
Q
What is the MOA of the carbonic anhydrase inhibitors? Which one do we need to know?
A
- Acetazolamide: oral, 500mg BID
- Potent competitive inhibitor of carbonic anhydrase
- Proximal tubule (10% distal tubule)
- Bicarbonate loss in the urine
2
Q
What is the net effect of the CA inhibitors?
A
- Alkaline urine due to Na-bicarbonate loss in urine
- Enhanced chloride reabsorption, resulting in hyperchloremic acidosis
3
Q
What are the clinical uses of the CA inhibitors?
A
- Diuretics: limited use
- Alkalinize tubular urine (cysteinurea)
- Reduce intra-ocular pressure (glaucoma)
- Management of seizures (unknown)
- Prophylactic (and management) for mountain sickness
4
Q
What are the side effects of Acetazolamide?
A
- Metabolic acidosis
- Markedly increase K+ loss in urine (acute effect)
5
Q
What is the MOA of the osmotic diuretics?
A
- Mannitol
- Osmotically inhibit Na/H2O reabsorption in the PCT
- Expand EC volume and INC renal medullary BF
- DEC medullary tonicity to impair ability of thin segments of loop of Henle to extract water and absorb NaCl
6
Q
What is the net effect of the osmotic diuretics?
A
- INC urine flow with small increments of Na, K, Cl
- Initially INC plasma vol and BP
7
Q
What are the clinical uses of Mannitol?
A
- Tx of dialysis disequilibrium syndrome
- Reduce intracranial pressure
- Reduce intraocular pressure
8
Q
What is the MOA of the loop diuretics?
A
- Furosemide, Bumetanide, Torsemide
- Inhibit NK2Cl symporter in thick ascending limb of LOH
- INC renal BF
- INC renal PG’s
- Stimulate renin release and maintain GFR
9
Q
What are the net effects of the loop diuretics?
A
- Copious diuresis with significant Na loss
- INC K, Ca, Mg secretion
- INC excretion of H+, resulting in mild metabolic alkalosis
10
Q
What is the therapeutic utility of the loop diuretics?
A
- Edema of cardiac, hepatic, and renal origin (oral)
- Acute pulmonary edema: given IV for rapid mobilization of edema fluid
11
Q
What is the MOA of the loop diuretics in pulmonary edema?
A
- DEC pulmonary wedge pressure
- Venodilation, so DEC left ventricular filling pressure
- INC compliance of pulmonary vasculature that facilitates mobilization of fluid
- Brisk copious diuresis
- Mobilization of calcium, as in hypercalcemia
- Maintenance of renal PG’s and renin to prevent renal failure
- Washout of toxins
- Anti-HTN, particularly when GFR very low
12
Q
What are the three examples of loop diuretics?
A
-
Furosemide: dilates veins, INC venous capacitance (DEC LV filling pressure)
1. Side effects: a) fluid and electrolyte imbalance, b) ototoxicity, c) INC BUN, hyperglycemia, hyperuricemia - Bumetanide: useful with Warfarin
- Torsemide: vasodilator
13
Q
What is the MOA and net effect of the thiazide diuretics?
A
- Hydrochlorothiazide, Chlorthalidone, Metolazone
- Inhibit Na/Cl transporter in early distal tubule
- Net effect: mild loss of sodium and water
- INC potassium excretion (hypokalemia)
- Potent: Metolazone, Quinothazone
14
Q
What is the therapeutic utility of the thiazides?
A
- Tx of mild to moderate edema
- Essential HTN
- Diabetes insipidus
- Hypercalciurea
15
Q
What are the side effects of the thiazides?
A
- Hypokalemia and hypmagnesemia
- Hyperuricemia, hypercalcemia, hyperglycemia
- Lipid disorders
