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The Renal System and Diuretics Pharmacology

One of your clinic patients is being treated with spironolactone. Which of the following statements best describes a property of this drug?

ExplanationSpironolactone is a potassium-sparing diuretic. Its active metabolite displaces aldosterone from aldosterone receptors in the collecting ducts. The drug is ineffective in the absence of aldosterone. (Recall that aldosterone normally causes renal Na + retention and K + loss. The effects of aldosterone are qualitatively the opposite: Na + loss, K + retention.) Owing to the ability of spironolactone to counteract the effects of aldosterone, it is particularly suited for patients with primary or secondary hyperaldosteronism (e.g., adrenal cortical tumor or hepatic dysfunction, as might occur with long-term/high-dose alcohol consumption, respectively). There is abundant data that the drug is beneficial in heart failure and probably reduces morbidity in severe heart failure. In addition to the potential for causing hyperkalemia (especially if combined with oral potassium supplements, which should not be done) and hyponatremia (overall risk is low), spironolactone may cause several other side effects. CNS side effects include lethargy, headache, drowsiness, and mental confusion. Other side effects that are fairly common arise from the drug’s androgen receptor–blocking actions: gynecomastia (in men and women) and erectile dysfunction. It may also cause seborrhea, acne, and coarsening of body hair. (Paradoxically, the drug can cause hirsutism in some patients, but it is also used to manage hirsutism in others.)