There is described a method of reducing drug liking a subject comprising the step of administering to the subject an oral pharmaceutical composition comprising: (i) hydromorphone or a pharmaceutically acceptable salt thereof, and (ii) naloxone or a pharmaceutically acceptable salt thereof, wherein the oral pharmaceutical composition comprising (i) and (ii) in a weight ratio equal to or less than about 4:1. There is also described use of an oral pharmaceutical composition comprising: (i) hydromorphone or a pharmaceutically acceptable salt thereof, and (ii) naloxone or a pharmaceutically acceptable salt thereof, wherein the oral pharmaceutical composition comprising (i) and (ii) in a weight ratio equal to or less than about 4:1, for reducing drug liking in a subject. The present inventors have conducted clinical studies from which it can be concluded that that drug liking in opioid abusers can be reduced when the weight ratio of (i) and (ii) in an intravenous composition is equal to or less than about 4:1. Based on the these clinical studies, the present inventors have established a reasonable inference that similar results would be obtained in the case of oral pharmaceutical compositions having a corresponding weight ratio of (i) and (ii) - i.e., if such an oral composition were to be abused by extraction of (i) and (ii) therefrom, the resulting extraction composition would behave in a similar manner as the intravenous compositions used in the clinical studies reported herein.
