Diuretics Flashcards
1
Q
Proximal Tubule Absorption
A
- Sodium chloride (active transport), water (passive transport), others (sodium bicarbonate glucose, amino acids, glucose); site of action of acetazolamide (CA inhibitor) and mannitol (osmotic diuretic)
2
Q
Loop of Henle Absorption
A
- Water is reabsorbed (osmotic forces) in the descending thin segment; site of action of mannitol. NaCl is reabsorbed (35%) in the thick segment and is impermeable to water; site of action of furosemide (loop diuretic), a Na/K/Cl cotransporter inhibitor.
3
Q
Distal Convuluted Tubule Absorption
A
- Approximately 10% of filtered NaCl is reabsorbed in the distal convoluted tubule and is relatively impermeable to water; site of action of Hydrochlorothiazide (thiazide), a Na/Cl co-transport inhibitor.
4
Q
Collecting Tubule Absorption
A
- Approx. 2-5% of filtered NaCl is reabsorbed in the collecting tubule; site of action of potassium-sparring diuretics, spironolactone (aldosterone receptor blocker) and amiloride (Na channel blocker). Collecting tubule is also the site of action of conivaptan (AntiDiuretic Hormone receptor antagonist), demeclocycline (AntiDiuretic Hormone cAMP antagonist) and mannitol.
5
Q
Major diuretic drugs which have been found to induce diuresis
A
- Carbonic anhydrase inhibitors
- Osmotic diuretics
- Loop diuretics
- Thiazides
- Potassium-sparring diuretics
- Antidiuretic hormone (ADH) antagonists
6
Q
Carbonic Anhydrase Inhibitors
A
- Acetazolamide
7
Q
Acetazolmide MOA
A
- Carbonic anhydrase inhibitors
- Inhibition of bicarbonic reabsorption
8
Q
Acetazolamide Pharmacodynamics
A
- Carbonic Anhydrase Inhibitor
- Diuretic efficiency decreases significantly over several days due to enhanced NaCl reabsorption by the remainder of the nephron.
9
Q
Acetazolamide Pharmacokinetics
A
- Carbonic Anhydrase Inhibitor
- Good oral bioavailability; diuresis is apparent within 30min., persists for 12hrs. after single dose, drug elimination by proximal tubule segment.
10
Q
Acetazolamide Adverse Reactions
A
- Hyperchloremic metabolic acidosis
- Renal stones
- Renal potassium wasting
- Other toxicities: hypersensitivity reactions
11
Q
Acetazolamide Therapeutic Uses
A
- Glaucoma- decreases aqueous humor and intraocular pressure
- Urinary alkalinization- enhance excretion of weak acids
- Metabolic alkalosis- diuretic therapy (w/ loop diuretics) during heart failure
- Acute mountain sickness
- Other uses: adjuvants for epilepsy
12
Q
Osmotic Diuretics
A
- Mannitol
13
Q
Mannitol MOA
A
- Osmotic Diuretics
- Prevents normal water reabsorption in the proximal tubule, descending limb of the loop of henle and collecting tubule due to osmotic forces. Also opposes the action of ADH in the collecting tubule.
14
Q
Mannitol Pharmacokinetics
A
- Osmotic Diuretic
- Poorly absorbed, must be given parentarally
15
Q
Mannitol Adverse Reactions
A
- Osmotic diuretic
- Extracellular volume expansion, may complicate heart failure and produce pulmonary edema
- Dehydration and hypernatremia