Mechanism of Action Spironolactone
Spironolactone (Aldactone) is structurally related to aldosterone and acts as a competitive inhibitor to prevent the binding of aldosterone to its specific cellular binding protein. Spironolactone thus blocks the hormone induced stimulation of protein synthesis necessary for Na+ reabsorption and K+ secretion. Spironolactone, in the presence of circulating aldosterone, promotes a modest increase in Na+ excretion associated with a decrease in K+ elimination.The observations that spironolactone is ineffective in adrenalectomized patients and that the actions of spironolactone can be reversed by raising circulating ldosterone blood levels (surmountable antagonism) support the conclusion that spironolactone acts by competitive inhibition of the binding of aldosterone with receptor sites in the target tissue. Spironolactone acts only when mineralocorticoids are present.
Clinical Uses Spironolactone
Spironolactone has been used clinically in the fol lowing conditions:
1. Primary hyperaldosteronism. Used as an aid in preparing patients with adrenal cortical tumors for surgery.
2. Hypokalemia.Used in patients with low serum K+ resulting from diuretic therapy with other agents.Its use should be restricted to patients who are unable to supplement their dietary K intake or adequately restrict their salt intake or who cannot tolerate orally available KCl preparations.
3. Hypertension and congestive heart failure.Although spironolactone may be useful in combination with thiazides, the latter remain the drugs of first choice. Fixed-dose combinations of spironolactone and a particular thiazide (e.g.,Aldactazide) generally offer no therapeutic advantage over either component given separately and tend to restrict the ability of the clinician to determine the optimal dosage of each drug for a particular patient.
,
4. Cirrhosis and nephrotic syndrome. Spironolactone is a mild diuretic and may be useful in treating the edema that occurs in these two clinical conditions,
that is, when excessive K+ loss is to be avoided.
Spironolactone (Aldactone) is structurally related to aldosterone and acts as a competitive inhibitor to prevent the binding of aldosterone to its specific cellular binding protein. Spironolactone thus blocks the hormone induced stimulation of protein synthesis necessary for Na+ reabsorption and K+ secretion. Spironolactone, in the presence of circulating aldosterone, promotes a modest increase in Na+ excretion associated with a decrease in K+ elimination.The observations that spironolactone is ineffective in adrenalectomized patients and that the actions of spironolactone can be reversed by raising circulating ldosterone blood levels (surmountable antagonism) support the conclusion that spironolactone acts by competitive inhibition of the binding of aldosterone with receptor sites in the target tissue. Spironolactone acts only when mineralocorticoids are present.
Clinical Uses Spironolactone
Spironolactone has been used clinically in the fol lowing conditions:
1. Primary hyperaldosteronism. Used as an aid in preparing patients with adrenal cortical tumors for surgery.
2. Hypokalemia.Used in patients with low serum K+ resulting from diuretic therapy with other agents.Its use should be restricted to patients who are unable to supplement their dietary K intake or adequately restrict their salt intake or who cannot tolerate orally available KCl preparations.
3. Hypertension and congestive heart failure.Although spironolactone may be useful in combination with thiazides, the latter remain the drugs of first choice. Fixed-dose combinations of spironolactone and a particular thiazide (e.g.,Aldactazide) generally offer no therapeutic advantage over either component given separately and tend to restrict the ability of the clinician to determine the optimal dosage of each drug for a particular patient.
,
4. Cirrhosis and nephrotic syndrome. Spironolactone is a mild diuretic and may be useful in treating the edema that occurs in these two clinical conditions,
that is, when excessive K+ loss is to be avoided.
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Unknown - Friday, 29 April 2011
