What are the 4 K sparing diuretics?
- Amiloride
- Triamterene
- Spironolactone
- Eplerenone
How do amiloride and triamterene work?
-Directly on renal tubules transport mechanisms in the convoluted tubules. (independent of aldosterone)
How do spironolactone and eplerenone work?
- Compete for aldosterone receptors in distal tubule to block Na reabsorption, and K secretion
- Works only when aldosterone is present
amiloride and triamterene does what to the elecctrolytes?
- Increase secretion of Na, chloride and Bicarb
- Increase in urine PH (alkaline)
How are amiloride and triamterene different?
- Amiloride is more potent
- Amiloride is incompletely absorbed / Triamterene is readily absorbed
- Amiloride is not metabolized / Triamterene is metabolized (metabolites)
- Elimination: amiloride 18 hours/ triantrene 3-5 hours
What are the uses K sparing diuretics?
-Used with Loops or Thiazides to augment diuresis and limit K loss
How do k sparing compare with other diuretics?
- Act more distally, and are less effective
- No hyperuricemia
How does aerosilized amiloride help cystic fibrosis?
-Improves sputum viscosity
What is the principle side effect with K sparing? And what drugs increase this problem?
- HyperK
- NSAIDs, ACEI, Beta blockers
How long will spironolactone take to work and last?
- 2-4 days to take full effect
- 48-72 hours after discontinuation
Spironolactone pharmacokinetics?
- 1st pass metabolism
- binds to plasma proteins
- Canrenone is major metabolite
What are the clinical uses of spironolactone?
- Edema due to CHF and cirrhosis
- Antihypertensive (used with thiazides)
What is the major side effect of spironolactone? and how do the side effects compare with thiazides side effects?
- Hyper K
- No hypoK, HyperMag, or Hyperurecimia
How does diamox (caronic anhydrase inhibitor) work?
- Inhibits carbonic anhhydrase in proximal renal tubules
- Excretion of H is diminished
- Loss of Bicarb
- Cl is retained (balance loss of bicarb)
- Excretion of K in exchange for Na
What is the overall net effect of diamox?
-Excretion of alkaline urine in a hyperchloremic metabolic acidosis
Acetazolamide (Diamox®) Diuretic action is not altered by _____ or _____ acidosis.
Metabolic / respiratory
What are the clinical uses of diamox?
- Altitude sickness
- Decrease IOP
- Decrease CSF
- Inhibit seizures
- Familial periodic paralysis
- stimulate ventilation in patients who are hypoventilating
How does diamox effect COPDers?
-Loss of bicarb may lead to respiratory acidosis leading to CNS depression
What are the dopamine receptor agonist drugs?
- Dopamine
- Fenoldapam
What does dopmaine receptor 1 do in the kidneys?
- Increase cAMP
- Vasodilate increasing RBF and GFR
- Inhibits Na reabsorption
- Promotes naturesis
What does dopmaine receptor 2 do in the kidneys?
-Inhibit NE release
What does low dose dopamine do? high dose?
- Low = DA1 and DA2
- High = Beta1 increase CO, renal perfusion and RBF
What receptors does fenoldopam work on?
- Post synaptic DA1
- Weak 5HT-3
What does fenoldopam infusion do?
- Renal vasodilation
- Increased RBF
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