For many years, urine alkalinization has been one of the cornerstones in the treatment of homozygous
cystinuria. Because of the relationship found between the excretion of urinary
sodium and
cystine,
potassium citrate has emerged as the preferred
sodium-free alkalizing agent. To evaluate the usefulness of
potassium citrate for urine alkalization in cystinuric patients,
sodium bicarbonate and
potassium citrate were compared in 14 patients (10 on
tiopronin treatment and four without treatment with
sulfhydryl compounds). The study started with 1 week without the use of any alkalizing agents (Period 0) followed by 2 weeks with
sodium bicarbonate (Period 1) and 2 weeks with
potassium citrate (Period 2). Urinary pH, volume, excretion of
sodium,
potassium, citrate and free
cystine, as well as the plasma
potassium concentration, were recorded.
Potassium citrate was shown to be effective as an alkalizing agent and, in this respect, not significantly different from
sodium bicarbonate. Even though a normal diet was used, a significant increase in urinary
sodium excretion was observed with
sodium bicarbonate (Period 1). Urinary
potassium and
citrate excretion increased with
potassium citrate (Period 2). A significant correlation was found between urinary
sodium and
cystine in the tio-pronin-treated patients. No significant differences in
cystine excretion were recorded in Periods 0, 1 and 2. Plasma
potassium was significantly higher during Period 2, but only one patient developed a mild
hyperkalemia (5.0 mmol/l). The use of
potassium citrate for urine alkalization in homozygous
cystinuria is effective and can be recommended in the absence of severe renal impairment.