Distal (Potassium Sparing) Diuretics

Agents:

spironolactone
triamterene

Mechanism of action

Inhibition of Na/K exchange at aldosterone dependent distal tubular site

Spironolactone - competes with aldosterone for regulatory site

Triamterene - decreases activity of pump directly
•    Either mechanism decreases potassium wasting
•    Either mechanism produces poor diuresis (when used alone)
o    relatively unimportant Na recovery site

Diurectic activity increased if:

•    sodium load (body) is high 
•    aldosterone concentrations are high 
•    sodium load (tubule) is high - secondary to diuresis

Other electrolytes unaffected

Toxicity

•    spironolactone may produce adrenal and sex hormone effects with LONG-TERM use
•    Both drugs may produce electrolyte imbalance