Pharmacokinetics of epidural butorphanol in isoflurane-anaesthetized dogs.
Sixteen healthy male dogs were used at random in this protocol. The dogs were anaesthetized with isoflurane in oxygen. Eight of the dogs received 0.25 mg/kg of butorphanol (group B) and the others an equal volume of isotonic saline (group S) administered by a catheter inserted in the lumbosacral epidural space. Butorphanol concentrations in plasma and cerebrospinal fluid (CSF) were measured using high-performance liquid chromatography with electrochemical detection. Maximum concentration of butorphanol and time to obtain this concentration were 42.28 ng/mL at 13.88 min in blood, and 18.03 ng/mL at 30 min in CSF. Volume of distribution, clearance, mean distribution and elimination half-lives were respectively 4.39 L/kg, 2.02 L/h.kg, 16.5 min and 189.1 min. Mean isoflurane minimal alveolar concentration values for group B obtained following hind- or forelimb stimulation decreased by 31% after epidural butorphanol. Cutaneous analgesia (to pin-prick test) persisted for 3 h after the end of isoflurane anaesthesia in group B and was in correlation with the plasmatic analgesic dose of butorphanol (9 ng/mL). These results suggested that analgesia was predominantly obtained by action of butorphanol on the supraspinal structures following its vascular systemic absorption.
Troncy
E
E
Département de sciences cliniques, Faculté de médecine vétérinaire, Université de Montrèal, Saint-Hyacinthe (Quebec), Canada.
Besner
J G
JG
Charbonneau
R
R
Cuvelliez
S G
SG
Blais
D
D
D015360:Analgesia, Epidural / Q000662:veterinary; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000097:blood / Q000134:cerebrospinal fluid / Q000493:pharmacokinetics*; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002077:Butorphanol / Q000008:administration & dosage / Q000097:blood / Q000134:cerebrospinal fluid / Q000493:pharmacokinetics*; D002851:Chromatography, High Pressure Liquid; D004285:Dogs; D004347:Drug Interactions; D004357:Drug Synergism; D006207:Half-Life; D007530:Isoflurane / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D010805:Physical Conditioning, Animal; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000378:metabolism
D000701:Analgesics, Opioid; D018685:Anesthetics, Inhalation; D007530:Isoflurane; D002077:Butorphanol