There were also differences in the pharmacokinetic parameters ( 95 % confidence interval ) of metformin between these two groups [ area under the concentration-time curve ( AUC ) 0 - 19.7 ( 15.7-23 .8 ) vs. 14.3 ( 11.7-16 .9 ) g h/L ; renal clearance ( CLr ) 16.8 ( 8.5-25 .0 ) vs. 34.1 ( 24.9-43 .2 ) L/h ; tubular secretion clearance ( CLt ) 8.1 ( 2.2-18 .1 ) vs. 22.7 ( 15.5-29 .8 ) L/h ; all P < 0.05 ] .