Antinociceptive Activity of and Clinical Experience with Buprenorphine in Swine

We performed antinociceptive testing on swine receiving buprenorphine. Intravenous access was achieved, and animals were allowed to recover for 24 h. Baseline skin-twitch latency to a focused light source was determined for each animal. Animals received intravenous (i.v.) buprenorphine at 0.08 (n =1), 0.16 (n = 1), 0.005 (n = 5), 0.01 (n = 5), or 0.02 mg/kg (n = 6). Skin-twitch latency was determined 15, 30, 60, 120, 180, 240, 300, 360, 420, 480, 540, and 600 min after buprenorphine administration. Analgesic activity as measured by a significant increase in latency time over baseline values occurred at all time points except 480 min in animals that received 0.02 mg/kg buprenorphine i.v. Analgesic activity to 420 min was demonstrated in animals that received 0.01 mg/kg buprenorphine i.v. Analgesic activity was not demonstrated at any time point in animals that received 0.005 mg/kg buprenorphine i.v. A retrospective analysis of postoperative care records was performed to determine whether 0.01 mg/kg buprenorphine i.v. or intramuscularly (i.m.) postoperatively to swine provided clinically relevant analgesia. Records of swine receiving buprenorphine from 1997 to 2000 were reviewed for indications of treatment failure, such as pain or a change in analgesic regimen from that used routinely. Treatment failure occurred in 18 of 416 (4.3%) cases treated with buprenorphine. This failure occurred in 17% of cases with problems categorized as inflammatory in nature and in 15.5% of those with systemic problems or organ failure. We concluded that antinociceptive testing predicted that buprenorphine administered at 0.01 mg/kg i.v. in swine likely would provide analgesic efficacy for 6 h and when administered at 0.02 mg/kg i.v. likely would provide 10 h analgesia. Clinical signs of pain in animals recovering from surgery were not observed in the majority of cases when buprenorphine was administered twice or thrice daily at 0.01 mg/kg i.m. or i.v. However, buprenorphine was less effective at treating signs of pain associated with inflammation, organ failure, or systemic disease than at ameliorating pain associated with surgical incisions and orthopedic, dental, and ophthalmic procedures.