1. To what class of drugs does triamterene belong?
    Potassium sparing diuretics.
  2. What are the indications for triamterene?
    Chronic liver failure, CHF, [combination?]
  3. 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.
  4. What influences the expression of ENaC?
    Aldosterone - a steroid hormone.
  5. 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.
  6. In addition to K being spared with triamterene, what other ion is also spared?
  7. What adverse effects may be associated with triamterene?
    • Folate antagonism (unique to triamterene)
    • Hyperkalemia (as K is spared)
    • Metabolic acidosis (as H+ is spared)
  8. What can be combined with triamterene to avoid potential for hyperkalemia?
    Thiazide or loop diuretics.
  9. What happens to the levels of the following in the ECF?

    Volume, NaCl, K, H
    • Increase: K, H
    • Decrease: Volume, NaCl
  10. What is the diuretic capacity of triamterene?
    About 3% NaCl (action is at the end of the nephron).
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