AIM:To investigate the therapeutic effect of enteric-coated sustained-release new dosage form of tadalafil on mice with renal fibrosis caused by unilateral ureteral obstruction(UUO).METHODS:Eight-week-old male C57BL/6J mice were divided into four groups randomly:sham group,UUO group,UUO+new dosage form of tadalafil(1 mg/kg)group and UUO+original patented drug of tadalafil(5 mg/kg)group.Surgery was performed to create a mouse UUO model,and therapeutic drugs were administered intragastrically for 7 d after modeling.A fully automated biochemi-cal analyzer was used to detect serum creatinine(SCr)levels of each group.Through renal histopathological staining(HE staining,Masson trichrome staining,and immunohistochemistry staining)and Western blot,we assessed the therapeutic effect of enteric-coated sustained-release new dosage forms of tadalafil on kidney fibrosis in mice,as well as its effect on the expression and distribution of fibronectin(FN)and α-smooth muscle actin(α-SMA).RESULTS:Compared with sham group,the SCr levels were significantly increased in mice with renal fibrosis,and renal tubules were dilated and in-filtrated with inflammation.Moreover,the expressions of FN and α-SMA were increased significantly(P<0.05).New dosage form and the original patented drug tadalafil both significantly reduced SCr levels in mice with renal fibrosis,im-proved the renal tissue structure on the affected side,reduced collagen fiber deposition,and inhibited FN and α-SMA ex-pression(P<0.05).CONCLUSION:Enteric-coated sustained-release new dosage form of tadalafil reduces the deposit of extracellular matrix in kidney interstitial tissue and attenuates fibrosis and renal function damage caused by ureteral ob-struction.New dosage form of tadalafil has significant advantages over the original patented drug because the low dose and high effectiveness.