SY-640 (Oral; 150 mg/kg; once daily for 7 days) significantly inhibits Propionibacterium acnes and Lipopolysaccharide-induced liver injury, but a single administration is without effect. SY-640 (p.o.; 150 mg/kg; once daily for three days) significantly increases the liver microsomal cytochrome P-450 content and aminopyrine demethylase activity in mice. The hepatic microsomal aminopyrine demethylase activity is obviously inhibited two hours after oral administration of SY-640.