The most common indication for butorphanol is management ofmigraine using the intranasal spray formulation. It may also be usedparenterally for management of moderate-to-severe pain, as a supplement for balanced generalanesthesia, and management of pain duringlabor. Butorphanol is also quite effective at reducing post-operative shivering (owing to its kappa agonist activity). Butorphanol is more effective in reducing pain in women than in men.[6]
Butorphanol exhibitspartial agonist andantagonist activity at theμ-opioid receptor, as well as partial agonist activity at theκ-opioid receptor (Ki = 2.5 nM;EC50 = 57 nM;Emax = 57%).[6][7] Stimulation of these receptors oncentral nervous systemneurons causes an intracellularinhibition ofadenylate cyclase, closing of influx membranecalcium channels, and opening of membranepotassium channels. This leads to hyperpolarization of the cellmembrane potential and suppression of action potential transmission of ascending pain pathways.Because of its κ-agonist activity, at analgesic doses butorphanol increases pulmonary arterial pressure and cardiac work. Additionally, κ-agonism can causedysphoria at therapeutic or supratherapeutic doses; this gives butorphanol a lower potential for abuse than other opioid drugs.[8]
Within theINN,USAN,BAN, andAAN naming systems this drug is known asbutorphanol, while withinJAN it is namedtorbugesic.[2][3][4] As thetartratesalt, butorphanol is known asbutorphanol tartrate (USAN,BAN).[2][3][4]
Butorphanol is listed under theSingle Convention on Narcotic Drugs 1961 and in the United States is aSchedule IV controlled substance with a DEA ACSCN of 9720.[9] The free base conversion ratio of the hydrochloride is 0.69.[10] Butorphanol was originally aSchedule II controlled substance and was later decontrolled at one point.[citation needed]
Inveterinary anesthesia, butorphanol (trade name: Torbugesic) is widely used as asedative and analgesic in dogs, cats and horses. For sedation, it may be combined with tranquilizers such as alpha-2 agonists (medetomidine),benzodiazepines, oracepromazine in dogs, cats and exotic animals. It is frequently combined withxylazine ordetomidine in horses.[11] Butorphanol may be administered intravenously, intramuscularly, subcutaneously, orper os. Intramuscular and subcutaneous administration may cause pain. Oral tablets have poor bioavailability and are not suitable for analgesia. Instranasal usage has been reported in parrots and rabbits.[12] Butorphanol when administered at 0.4 mg/kg given IV/IM does not provide sufficient post-operative analgesia forlaparotomy and shoulderarthrotomy in dogs and ovariohysterectomy in bitches.[12][13][14][15] When butorphanol is used as a sedative in dogs—either on its own or withdexmedetomidine—it provides fast sedation and is faster than sedation withmethadone.[12][16][17] Butorphanol is also approved as anantitussive in the dog.[12]
Butorphanol has antiemetic properties, which counteracts the nausea-induced by dexmedetomidine.[18][12] Butorphanol's antiemetic properties are greater than that ofbuprenorphine.[12][19] Doses of 0.1–0.4 mg/kg IM in cats provides appropriate sedation but greater sedation may be achieved with full μ-opioid receptor agonists.[20] Butorphanol when administered alongsidemeloxicam,lidocaine, anddexmedetomidine provides appropriate analgesia for orchidectomy and reduces themean alveolar concentration forisoflurane more than buprenorphine. Butorphanol can reduce the MAC 23–68%.[12][21][22]
As a mixed agonist-antagonist butorphanol can reverse some effects of full-opioid such as bradycardia and respiratory depression whilst maintaining analgesia.[12]
Although butorphanol is commonly used for pain relief in reptiles, no studies (as of 2014) have conclusively shown that it is an effective analgesic in reptiles.[23]
Butorphanol is a narcotic used for pain relief in horses.[24] It is administered either IM or IV, with its analgesic properties beginning to take effect about 15 minutes after injection and lasting 4 hours.[25][12] In healthy horses butorphanol increases locomotive activity, but the administration of a sedative e.g.xylazine oracepromazine prevents locomotion. In neonatal foals this effect is not observed and instead butorphanol produces sedation.[26] Pre-operative butorphanol administered intravenously at 0.02–0.1 mg/kg provides adequate post-operative analgesia for elective surgeries;[12][27][28] however, one study found that pre-operative butorphanol (0.01 mg/kg IV) combined withdetomidine did not provide adequate post-operative analgesia.[29][12]
^abGear RW, Miaskowski C, Gordon NC, Paul SM, Heller PH, Levine JD (November 1999). "The kappa opioid nalbuphine produces gender- and dose-dependent analgesia and antianalgesia in patients with postoperative pain".Pain.83 (2):339–45.doi:10.1016/S0304-3959(99)00119-0.PMID10534607.S2CID31025735.
^Compendium of Data sheets for Animal Medicines. 2005. National Office of Animal Health. October 2004.ISBN978-0-9548037-0-4.
^abcdefghijkSimon BT, Lizarraga I (11 September 2024). "Opioids". In Lamont L, Grimm K, Robertson S, Love L, Schroeder C (eds.).Veterinary Anesthesia and Analgesia, The 6th Edition of Lumb and Jones. Wiley Blackwell. pp. 382–383.ISBN978-1-119-83027-6.
^Gültiken N, Gürler H, Yarım GF, Binli F, Tuncay M, Büyükbudak F, et al. (September 2022). "Antioxidant and analgesic potential of butorphanol in dogs undergoing ovariohysterectomy".Theriogenology.190:1–7.doi:10.1016/j.theriogenology.2022.07.002.PMID35849850.
^Gomes VH, Barbosa DJ, Motta AS, Corrêa CG, Moreno DJ, da Silva MF (November 2020). "Evaluation of nalbuphine, butorphanol and morphine in dogs during ovariohysterectomy and on early postoperative pain".Veterinary Anaesthesia and Analgesia.47 (6):803–809.doi:10.1016/j.vaa.2020.07.035.PMID32891492.
^Trimble T, Bhalla RJ, Leece EA (September 2018). "Comparison of sedation in dogs: methadone or butorphanol in combination with dexmedetomidine intravenously".Veterinary Anaesthesia and Analgesia.45 (5):597–603.doi:10.1016/j.vaa.2018.03.008.PMID30077553.
^Papastefanou AK, Galatos AD, Pappa E, Lymperis AG, Kostoulas P (November 2015). "The effect of butorphanol on the incidence of dexmedetomidine-induced emesis in cats".Veterinary Anaesthesia and Analgesia.42 (6):608–613.doi:10.1111/vaa.12260.PMID25819160.
^Sladky KK (2014). "Chapter 18: Analgesia". In Mader DR, Divers SJ (eds.).Current therapy in reptile medicine & surgery. Elsevier Health Sciences. pp. 217–229.ISBN978-0-323-24293-6.
^Reed R, Trenholme N, Skrzypczak H, Chang K, Ishikawa Y, Barletta M, et al. (September 2022). "Comparison of hydromorphone and butorphanol for management of pain in equine patients undergoing elective arthroscopy: a randomized clinical trial".Veterinary Anaesthesia and Analgesia.49 (5):490–498.doi:10.1016/j.vaa.2022.05.006.PMID35752564.S2CID249353700.
^Kalpravidh M, Lumb WV, Wright M, Heath RB (February 1984). "Analgesic effects of butorphanol in horses: dose-response studies".American Journal of Veterinary Research.45 (2):211–216.doi:10.2460/ajvr.1984.45.02.211.PMID6711944.
^Taylor PM, Clark C, Whay HR, Murrell J, Love EJ (2009). "Analgesic effect of butorphanol in ponies following castration".Equine Veterinary Journal.41 (6). Wiley:552–556.doi:10.2746/042516409x391024.ISSN0425-1644.PMID19803050.
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