The mean time to reach a stable dose in the study group and the control group was ( 16.8 1.5 ) and ( 25.6 1.8 ) days , and the median time was ( 11.0 1.0 ) days and ( 20.0 2.0 ) days , the difference between the 2 groups being statistically significant ( ( 2 ) = 18.175 , P < 0.001 ) .