A therapeutic drug for chronic renal failure in mammals including cats, and a treatment method thereof are provided. By administrating a compound represented by the formula (I) below at a dose of 55 μg per administration, or 6 to 26.4 μg/kg per administration, preferably twice a day for not less than 30 days orally and daily, the increase in BUN, SCre or the like which is a marker of renal function can be suppressed to stabilize the value thereof and chronic renal failure can be ameliorated.本發明提供一種以貓為代表之哺乳動物之慢性腎衰竭之治療藥與其處理方法。藉由將下述通式(I)所表示之化合物以經口之方式每次投予55μg、或每次投予6~26.4μg/kg、較佳為1天2次連日投予30天以上,可抑制作為腎功能標記物之BUN、SCre等之上升,實現穩定化,改善慢性腎衰竭。
