Cases 1 :
One of your clinic patients is being treated with spironolactone.
Which of the following statements best describes a property of this drug?
a. Contraindicated in heart failure, especially if severe
b. Inhibits Na+ reabsorption in the proximal renal tubule of the nephron
c. Interferes with aldosterone synthesis
d. Is a rational choice for a patient with an adrenal cortical tumor
e. Is more efficacious than hydrochlorothiazide in all patients who receive the
drug
The answer is d. (Brunton, pp 759–762; Craig, pp 247–248; Katzung,
pp 250–252.)
Spironolactone 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.)
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