A comparison of the effects of potassium citrate and sodium bicarbonate in the alkalinization of urine in homozygous cystinuria

Abstract

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.