Potassium Sparing Diuretics

These diuretics are the sodium channel blockers amiloride and triamterene and the antialdosterone spironolactone. They all have weak natriuretic effects and are antikaliuretic (see Fig. 6). Spironolactone is specifically indicated in hypertension due to primary mineralocorticoid excess, although in adrenal hyperplasia and hyperaldosteronism amiloride may prove more effective in maintaining plasma potassium and controlling BP. The main problem with spironolactone is that doses above 100 mg daily are usually poorly tolerated because of nausea and gynecomastia in men, although it does have a useful antiacne and antiandrogen effect in some women (e.g., polycystic ovary disease). Moreover, there is concern that long-term use may be associated with an increased risk of hematological malignancy. These agents are more commonly used to prevent thiazide and loop diuretic induced hypokalemia, particularly in patients on digoxin or with ischemic heart disease and a history of life-threatening cardiac dysrhythmias. It is worth noting that such combination diuretics were used in the trials of hypertension in the elderly (SHEP study, Dyazide; MRC study, Mod-uretic) and they were associated with significant reductions in the risk of stroke and myocardial infarction. However, they should be avoided in patients with significant renal impairment, because of their accumulation and the increased risk of hyperkalemia; and they must be used cautiously in diabetics in whom hyperkalemia is also a risk, especially in those patients with underlying hypo-reninemic hypoaldosteronsism (type IV renal tubular acidosis).

Nonsteroidal antiinflammatory drugs (e.g., indomethacin) antagonize the natriuretic action of thiazide and loop diuretics, and their sodium-retaining effect can impair the antihypertensive effect of thiazides (and other antihypertensives). In combination with potassium-sparing diuretics they may cause hyperkalemia.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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