Analgesic efficacy of butorphanol and morphine in bearded dragons and corn snakes.
OBJECTIVE
To test the hypothesis that administration of butorphanol or morphine induces antinociception in bearded dragons and corn snakes.


METHODS
Prospective crossover study.


METHODS
12 juvenile and adult bearded dragons and 13 corn snakes.


METHODS
Infrared heat stimuli were applied to the plantar surface of bearded dragon hind limbs or the ventral surface of corn snake tails. Thermal withdrawal latencies (TWDLs) were measured before (baseline) and after SC administration of physiologic saline (0.9% NaCl) solution (equivalent volume to opioid volumes), butorphanol tartrate (2 or 20 mg/kg [0.91 or 9.1 mg/lb]), or morphine sulfate (1, 5, 10, 20, or 40 mg/kg [0.45, 2.27, 4.5, 9.1, or 18.2 mg/lb]).


RESULTS
For bearded dragons, butorphanol (2 or 20 mg/kg) did not alter hind limb TWDLs at 2 to 24 hours after administration. However, at 8 hours after administration, morphine (10 and 20 mg/kg) significantly increased hind limb TWDLs from baseline values (mean +/- SEM maximum increase, 2.7+/-0.4 seconds and 2.8+/-0.9 seconds, respectively). For corn snakes, butorphanol (20 mg/kg) significantly increased tail TWDLs at 8 hours after administration (maximum increase from baseline value, 3.0+/-0.8 seconds); the low dose had no effect. Morphine injections did not increase tail TWDLs at 2 to 24 hours after administration.


CONCLUSIONS
Compared with doses used in most mammalian species, high doses of morphine (but not butorphanol) induced analgesia in bearded dragons, whereas high doses of butorphanol (but not morphine) induced analgesia in corn snakes.
Sladky
Kurt K
KK
Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706, USA.
Kinney
Matthew E
ME
Johnson
Stephen M
SM
D000701:Analgesics, Opioid / Q000009:adverse effects / Q000494:pharmacology*; D000818:Animals; D002077:Butorphanol / Q000009:adverse effects / Q000494:pharmacology*; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D008116:Lizards / Q000502:physiology*; D009020:Morphine / Q000009:adverse effects / Q000494:pharmacology*; D010146:Pain / Q000517:prevention & control / Q000662:veterinary; D010147:Pain Measurement / Q000662:veterinary; D012119:Respiration / Q000187:drug effects; D012911:Snakes / Q000502:physiology*; D013045:Species Specificity; D013997:Time Factors
D000701:Analgesics, Opioid; D009020:Morphine; D002077:Butorphanol