檸檬酸目前被認為是抑制尿石形成的抑制物之一，也是臨床上預防結石最方便、最有效的藥物之一。低檸檬酸尿結石症(原發性徎併發其他病因)約佔尿石生理性異常之50％左右。因此，若能服用藥物使尿中之酸鹼值和檸檬酸提高，將可預防大部份的尿路結石。 U-citra係含檸檬酸之製劑，是否有預防尿石之作用及其體內代謝之速度，我們以下列方式進行研究。⑴尿石病人 (低檸檬尿結石症) 10位，經〔尿石之新陳代謝評估〕後，給予 U-citra二週，每日三次，每次 30mEq ，服完第一週後，進行二次之〔尿石新陳代謝評估〕，比較尿液之致石成份之變化。⑵志願者(無尿石病史或尿路感染者)10位，經詳細解說後，要求收集24小時尿液，其中前8小時是每2小時為一時段收集，後16小時則是7小時和9小時為一時段收集，共六時段，再分別分析其中之 pH、鉀、檸檬酸。一週後，服用 30mEq後，重覆以上步驟。比較各時段之尿液變化。結果發現，⑴ U-citra使病人尿液之pH值昇高，檸檬酸及鉀離子有意義昇高。⑵ U-citra使志願者之尿液pH值，檸檬酸在前4小時內，鉀離子在前6小時內呈有意義昇高。除兩位病人有輕微上腸道不適外，無任何心肺血管方面不適之副作用。結論是U-citra能提昇尿液pH值及檸檬酸，故應有預防尿石之效果，唯其代謝快速，故在服用時其間距宜縮短。

Citrate, one of the recognized inhibitors of uninary stone formation, has been considered most convenient and effective in clinical use. To investigate this possibility, U-citra, a kind of granule preparation of potassium citrate manufactured in Taiwan, R.O.C. was used to study the physiological effect for prevention of stone recurrence and the pharmacokinetics (metabolism). The subjests were divided into 2 groups. ⑴ Hypocitraturia group: 10 patients were selected by metabolic evaluation of urolithiasis with urinary citrate below 250 mg/day. U-citra was administered at 30mEq tid for two weeks. Another metabolic evaluation of urolithiasis for comparison of urinary chemistry was performed one week after the initiation of treatment. ⑵ Normal volunteers group: 24-hour urine aws collected at 6 intervals (every 2-hour for the first 8 hours, 7-and 9-hour for the other 16 hours ). One week later, 30 mEq of U-citra was administerd, and another 6-time interval urine collection was completed. The urinary pH, potassium,calcium, citrate and creatinine were measured and compared in-between. This study indicates U-citra increased urinary pH, citrate as well as potassium in hypocitraturic patients. Moreover, U-citra raised urinary pH and citrate significantly in the first 4 hours and urinary potassium in the first 6 hours. No major side effects oc-curred except 2 minor gastrointestinal upsets in hypocitraturic patients. In conclusion, U-citra may prevent recurrence of urolithiasis. However, the interval of adminstration should be shortend because of its rapid metabolism. (J Urol R.O.C., 2:432-437, 1991)