Анотация: OBJECTIVE To evaluate antinociceptive effects of IV administration of hydromorphone alone or followed by buprenorphine or butorphanol to cats. ANIMALS 6 healthy adult cats. PROCEDURES In a randomized, blinded crossover design, cats received each of 4 treatments in which 2 IV injections were given 30 minutes apart: 2 of saline solution (Sal-Sal) or I each of hydromorphone HCI and saline solution (H-Sal), hydromorphone and buprenorphine HCI (H-Bupre), or hydromorphone and butorphanol tartrate (H-Butor). Skin temperature and thermal threshold were recorded before (baseline) and for 12 hours after the first injection. Percentage of maximum possible effect and thermal excursion (TE) were compared among treatments and measurement points. RESULTS Compared with baseline values, skin temperature was higher from 0.75 to 2 hours after the first injection for H-Sal; at 0.5, 1, 3, and 4 hours for H-Bupre; from 0.5 to 3 hours for H-Butor; and from 0.5 to I hours for Sal-Sal. Thermal excursion was higher than at baseline from 0.25 to 2 hours for H-Sal and H-Bupre and 0.25 to 0.75 hours for H-Butor ONCLUSIONS AND CLINICAL RELEVANCE Butorphanol administration decreased the duration of antinociception achieved with hydromorphone administration in cats .This opioid interaction and its impact on pain management require additional investigation