All of the following are true regarding diuretics except (DNB Dec 2011)
|A||Spironolactone is associated with hypokalemia|
|B||Acetazolamide inhibits carbonic anhydrase|
|C||Furosemide causes hypokalemia|
|D||Thiazides causes hypercalcemia|
a. Spironolactone is a steroid, chemically related to the mineralocorticoid aldosterone. Aldosterone acts on distal tubule and collecting duct cells by combining with an 'intracellular' mineralocorticoid receptor which induces the formation of aldosterone induced proteins (AlPs) which promote sodium ion reabsorption by a number of mechanisms and potassium ion secretion.
b. Spironolactone acts from the interstitial side of the tubular cells; combines with the mineralocorticoid receptors and inhibits the formation of AlPs in a competitive manner. Spironolactone is a mild saluretic because majority of sodium ions have already been reabsorbed proximal to its site of action. However, it antagonizes potassium ion loss induced by other diuretics and slightly adds to their natriuretic effect.
c. The potassium ion retaining action develops over 2 - 3 days. It increases calcium ion excretion by a direct action on renal tubules. Most severe adverse effect is hyperkalemia that may occur, especially if renal Junction is inadequate.