A method of inhibiting or reducing occurrence or intensity of pruritus including administering to a patient an effective amount of one or more of the morphinan derivative having a nitrogen-containing cyclic group of the Formula (Ia): wherein R1 is cyclopropylmethyl; R2 and R3 are independently hydrogen, hydroxy, C1-C5 alkoxy, C3-C7 alkenyloxy, C7-C13 aralkyloxy or C1-C5 alkanoyloxy; and the Formula (Ia) includes (+), (−) and (±) isomers or the pharmaceutically acceptable acid addition salt thereof.