Significance of measuring the uric acid / creatinine ratio (UUA / UCr) of spot urine during uric acid-lowering therapy

• Published in: Gout and Uric & Nucleic Acids Vol. 46; no. 1; pp. 37 - 44
• Main Authors: Ooyama, Hiroshi, Ooyama, Keiko, Moromizato, Hitoshi, Tabuchi, Daiki, Fujimori, Shin
• Format: Journal Article
• Language: Japanese
• Published: Japanese Society of Gout and Uric & Nucleic Acids 25.07.2022
• Subjects: benzbromarone; dotinurad; febuxostat; FEUA; UUA/UCr
• ISSN: 2435-0095
• DOI: 10.14867/gnamtsunyo.46.1_37

We measured the uric acid / creatinine ratio (UUA / Ucr) and uric acid excretion fraction (FEUA) of spot urine in patients (108 treated with dotinurad, 62 treated with benzbromarone, and 56 treated with febuxostat), when the serum uric acid level was 6 mg / dL or lower. Then, we investigated the differences in UUA / Ucr and FEUA among patients receiving the three drugs. The serum uric acid level and UUA/Ucr and FEUA were 5.3 ± 0.6 mg / dL, 0.504 ± 0.211, and 8.5 ± 4.1% in the dotinurad-treated group (daily dose of 1.1 ± 0.7 mg), 5.0 ± 0.6 mg / dL, 0.541 ± 0.210, and 9.8 ± 3.7% in the benzbromarone-treated group (daily dose of 48.8 ± 22.3 mg), and 5.1 ± 0.7 mg / dL, 0.215 ± 0.079, and 4.0 ± 1.1% in febuxostat-treated group (daily dose of 31.1 ± 13.6 mg), respectively. UUA / Ccr and FEUA were significantly lower in the febuxostat-treated group than in the two uricosuric drug-treated groups. There was a weak positive correlation between drug dose and UUA / Ccr in the dotinurad-treated group, but there was no correlation between drug dose and UUA / Ccr in the benzbromarone-treated group. It is considered that reason why UUA / UCr of patients taking uricosuric drugs as outpatients is not constant may be due to variable intake of food purine. When UUA / gCr corrected with g-creatinine (gCr) is expressed as 24-hour urinary uric acid excretion, there are some patients whose 24-hour urinary uric acid excretion exceeds 800 mg / day, considered to be a risk for urinary stones with uricosuric drugs such as dotinurad and benzbromarone. In the future, it will be necessary to verify the association between uric acid excretion and food purine intake in patients treated with uricosuric drugs, and even if the serum uric acid level is maintained at the target value by the uricosuric drugs, may be necessary to continue dietary treatment including the restriction of food purine intake in consideration of the level of urinary uric acid excretion.