FURESIS COMP

Furosemide inhibits active chloride transport in the thick ascending limb. Re-absorption of sodium, chloride from the nephron is reduced and a hypotonic or isotonic urine produced. The evidence from many experimental studies suggests that furosemide acts along the entire nephron with the exception of the distal exchange site.

Triamterene is a potassium-sparing agent. Triamterene inhibits the reabsorption of sodium ions in exchange for potassium and hydrogen ions at that segment of the distal tubule under the control of adrenal mineralocorticoids (especially aldosterone). The fraction of filtered sodium reaching this distal tubular exchange site is relatively small, and the amount which is exchanged depends on the level of mineralocorticoid activity. Thus, the degree of natriuresis and diuresis produced by inhibition of the exchange mechanism is necessarily limited.