The geometric mean ratios ( MPH-MLR/IR methylphenidate [ 90 % CI ] ) of log-transformed area under the plasma drug concentration-time curve to the last measurable observation ( day 1 : 0.88 [ 84.75-91 .80 ] ; day 4 : 0.84 [ 81.16-86 .94 ] ) , and area under the plasma drug concentration extrapolated to infinity ( day 1 : 0.93 [ 88.57-97 .28 ] ; day 4 : 0.88 [ 84.48-91 .17 ] ) were within the 80-125 % bioequivalence range .