Potassium-sparing diuretics act primarily in the collecting distal duct renal tubules to promote sodium and water excretion and potassium retention. The drugs interfere with the sodium-potassium pump that is controlled by mineralo-corticoid hormone aldosterone (sodium retained and potassium excreted). Potassium is reabsorbed and sodium is excreted.
Potassium-sparing diuretics are weaker than thiazides and loops and are used as mild diuretics or in combination with antihypertensive drugs. Continuous use of potassium-wasting diuretics requires a daily oral potassium supplement because potassium, sodium, and body water are excreted through the kidneys. However, potassium supplements are not used when the patient takes potassium-sparing diuretics.
When potassium-sparing diuretics are used alone they are less effective in reducing body fluid and sodium than when used in combination. They are usually combined with a potassium-wasting diuretic, such as a thiazide or loop. The combination intensifies the diuretic effect and prevents potassium loss. The main side effect of these drugs is hyperkalemia.
Caution should be used with patients who have poor kidney function. Urine output should be at least 600 mL per day. Patients should not use potassium supplements while taking this group of diuretics. If given with an ACE inhibitor, hyperkalemia could become severe or life-threatening because both drugs retain potassium. Gastrointestinal disturbances (anorexia, nausea, vomiting, diarrhea) can occur.
A list of potassium-sparing diuretic drugs is provided in the Appendix. Detailed tables show doses, recommendations, expectations, side effects, contraindications, and more; available on the book's Web site (see URL in Appendix).
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