Hyperkalemia mineralocorticoid receptor

ACE inhibitors do not completely block aldosterone synthesis. Since this steroid hormone is a potent inducer of fibrosis in the heart, specific antagonists, such as spironolactone and eplerenone, have recently been very successfully used in clinical trials in addition to ACE inhibitors to treat congestive heart failure [5]. Formerly, these drugs have only been applied as potassium-saving diuretics in oedematous diseases, hypertension, and hypokalemia as well as in primary hyperaldosteronism. Possible side effects of aldosterone antagonists include hyperkalemia and, in case of spironolactone, which is less specific for the mineralocorticoid receptor than eplerenone, also antiandrogenic and progestational actions. 

These diuretics act by reducing sodium reabsorption in the collecting duct, and hence increasing potassium retention. Spironolactone acts as a competitive antagonist of aldosterone, blocking its stimulatory effects on sodium reabsorption via the mineralocorticoid receptor. Amiloride and triamterene both inhibit ENaC, The danger of this group of diuretics is that they can induce hyperkalemia, which is particularly lilcely to occur in patients with kidney disease. 

The sample of patients selected for a clinical trial may not be representative of the entire population of patients with that disease. Patients entered into a trial usually are selected according to the severity of their disease and other characteristics inclusion criteria) or are excluded because of coexisting disease, concurrent therapy, or specific features of the disease itself (exclusion criteria). It always is important to ascertain that the clinical characteristics of an individual patient correspond with those of patients in the trial. For example, the Randomized Aldactone Evaluation Study (RALES) showed that treatment with the mineralocorticoid-receptor antagonist spironolactone was associated with a 30% reduction in death in patients with severe congestive heart failure. Hyperkalemia, a potential adverse effect, was seen only rarely in this study, which excluded patients with serum creatinine levels >2.5 mg/dL. With the expanded use of spironolactone after RALES was published, numerous patients, many of whom did not meet the RALES inclusion criteria, developed severe hyperkalemia. Therefore, knowledge of the criteria for selecting the patients in a trial must inform the application of study results to a given patient. 

---