Comments on spironolactone
Spironolactone
is a steroid-like molecule which is competitive inhibitor of aldosterone and other
mineralocorticoids. It acts in the distal renal tubule to interfere with aldosterone
mediated effects on sodium and potassium. However, spironolactone is not a particularly
effective diuretic. It inhibits reabsorption of less than 2% of filtered sodium. It is
most effective in clinical conditions associated with high circulating levels of
aldosterone such as is seen in with nephrotic syndrome, congestive heart failure, and
hepatic diseases with ascites (Wahlig. Pediatr Clin N A 1992; 19:251). The major
use of this diuretic is to prevent urinary losses of potassium induced by other diuretics
(Chemtob, Pediatr Clin N A 1989; 36:1231-50). Spironolactone is contraindicated in
the presence of anuria or hyperkalemia. The monitoring of serum potassium levels is
critical when treating an infant with spironolactone. As such, it does not produce a
large diuresis (at this point most of the sodium has already been reabsorbed). When other
diuretics are used though, larger amounts of sodium can be delivered to the distal tubule.
See diuretic for comparisons of
the effects and complications of the different diuretics. Once started, the effect of
the drug may not be seen for 2 to 3 days since it depends upon the synthesis of a peptide
which interacts with aldosterone. Once the drug is stopped, there is also a delay of
several days before the drug's activity diminishes because of the persistence of these
peptides. The half-life reported for healthy adults varies from 10 to 25 hours, however
there are no pharmacokinetic studies in infants. Scattered reports have shown that
spironolactone improves diuresis in children with liver disease, infants with congestive
heart failure secondary to congenital heart disease, or in infants with cor pulmonale
secondary to BPD. One would expect that the effects would be increased with significant
liver or renal disease (Roberts. Drug Therapy in Infants. Philadelphia: W. B.
Saunders, 1984:243-44).