Supersaturation of urine with uric acid and urate: response to a uricosuric diuretic

In order to assess the possibility that treatment with the uricosuric diuretic ticrynafen (tienilic acid) could lead to UA or MSU crystalluria, the degree of urinary supersaturation with respect to these crystalloids was assessed in persons receiving the diuretic for 1 week, and the results were compared with similar data generated from the use of probenecid. Initially, only probenecid significantly increased the degree of urinary supersaturation with respect to MSU, and after adjustment of urine pH values to 5.5, probenecid also increased the degree of urinary supersaturation with respect to nonionized UA. At a pH of 5.5, the urine was significantly more supersaturated with nonionized UA after a single dose of probenecid than after ticrynafen (tienilic acid). Ticrynafen never significantly affected the degree of urinary supersaturation with respect to UA or MSU. Neither agent affected small amounts of "colloidal" or "bound" urinary urate. Insofar as the degree of urinary supersaturation with these crystalloids predisposes to crystalluria and calculus formation, ticrynafen (tienilic acid) appears to present no increased risk.