Captopril reduces urinary cystine excretion in cystinuria
J. A. Sloand and J. L. Izzo Jr
Cystinuria is characterized by cystine stone formation and loss of renal
function. Conservative therapy is generally ineffective and penicillamine
therapy can be complicated by serious side effects. To our knowledge, we
report the first clinical use of captopril in the treatment of homozygous
cystinuria in two siblings. In the first patient, a 70% reduction in
cystine excretion was observed after 26 weeks of therapy with 150 mg/d of
captopril. Discontinuation of use of the drug resulted in a return to
baseline cystine excretion, further loss of renal function, and nephrotic
range proteinuria. Repeated treatment with captopril stabilized renal
function, reduced proteinuria, and returned cystine excretion to near
normal levels. In the second patient, cystine excretion was reduced by 93%
after nine weeks of therapy with 75 mg/d of captopril. No adverse side
effects were observed in either patient. Formation of the
captopril-cysteine disulfide accounts for part of the reduction in cystine
excretion but other mechanisms probably contribute. Because
captopril-cysteine disulfide is 200 times more soluble than cystine,
long-term captopril therapy may be useful in the treatment of cystinuria.
