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To what class of drugs does triamterene belong?
Potassium sparing diuretics.
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What are the indications for triamterene?
Chronic liver failure, CHF, [combination?]
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What is the target MOA of triamterene? Where is its site of action in the nephron?
- Blocker of epithelial Na channel (ENaC).
- [Late distal tubule?] and collecting duct.
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What influences the expression of ENaC?
Aldosterone - a steroid hormone.
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How does triamterene spare the loss of K while still acting as a diuretic?
By blocking ENaC, Na is not reabsorbed and pulls H2O with it as it is excreted in the urine. K does not diffuse out of the cell due to the net positive charge in the lumen from the excreted Na.
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In addition to K being spared with triamterene, what other ion is also spared?
Hydrogen
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What adverse effects may be associated with triamterene?
- Folate antagonism (unique to triamterene)
- Hyperkalemia (as K is spared)
- Metabolic acidosis (as H+ is spared)
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What can be combined with triamterene to avoid potential for hyperkalemia?
Thiazide or loop diuretics.
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What happens to the levels of the following in the ECF?
Volume, NaCl, K, H
- Increase: K, H
- Decrease: Volume, NaCl
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What is the diuretic capacity of triamterene?
About 3% NaCl (action is at the end of the nephron).
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