The duration of analgesia ( mean [ 95 % confidence interval ] ) was prolonged in the DexIV group ( 25 hours [ 17.632.4 ] ) compared with Control ( 13.2 hours [ 11.515.0 ] ; P < 0.001 ) but similar to the DexP group ( 25 hours [ 19.530.5 ] ; P = 1 ) .