Effects of methadone, alone or in combination with acepromazine or xylazine, on sedation and physiologic values in dogs.
OBJECTIVE
To evaluate the effects of methadone, administered alone or in combination with acepromazine or xylazine, on sedation and on physiologic values in dogs.


METHODS
Randomized cross-over design.


METHODS
Six adult healthy mixed-breed dogs weighing 13.5 +/- 4.9 kg.


METHODS
Dogs were injected intramuscularly with physiologic saline (Control), or methadone (0.5mg kg(-1)) or acepromazine (0.1 mg kg(-1)) or xylazine (1.0 mg kg(-1)), or acepromazine (0.05 mg kg(-1)) plus methadone (0.5 mg kg(-1)) or xylazine (0.5 mg kg(-1)) plus methadone (0.5 mg kg(-1)) in a randomized cross-over design, with at least 1-week intervals. Sedation, pulse rate, indirect systolic arterial pressure, respiratory rate (RR), body temperature and pedal withdrawal reflex were evaluated before and at 15-minute intervals for 90 minutes after treatment.


RESULTS
Sedation was greater in dogs receiving xylazine alone, xylazine plus methadone and acepromazine plus methadone. Peak sedative effect occurred within 30 minutes of treatment administration. Pulse rate was lower in dogs that received xylazine either alone or with methadone during most of the study. Systolic arterial pressure decreased only in dogs receiving acepromazine alone. When methadone was administered alone, RR was higher than in other treatments during most of the study and a high prevalence of panting was observed. In all treatments body temperature decreased, this effect being more pronounced in dogs receiving methadone alone or in combination with acepromazine. Pedal withdrawal reflex was absent in four dogs receiving methadone plus xylazine but not in any dog in the remaining treatments.


CONCLUSIONS
Methadone alone produces mild sedation and a high prevalence of panting. Greater sedation was achieved when methadone was used in combination with acepromazine or xylazine. The combination xylazine-methadone appears to result in better analgesia than xylazine administered alone. Both combinations of methadone/sedative were considered effective for premedication in dogs.
Faculdade de Medicina Veterinária, Centro Universitário de Maringá (CESUMAR), Maringá, Paraná, Brazil. btraposo@hotmail.com
Eduardo R
ER
Monteiro
Christian D N
CD
Figueroa
Jeison C
JC
Choma
Daniela
D
Campagnol
Carlos M
CM
Bettini
D000075:Acepromazine / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D016292:Procedural Sedation / Q000662:veterinary*; D018592:Cross-Over Studies; D004285:Dogs; D004359:Drug Therapy, Combination; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006993:Hypnotics and Sedatives / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008691:Methadone / Q000008:administration & dosage / Q000494:pharmacology*; D012119:Respiration / Q000187:drug effects; D014991:Xylazine / Q000008:administration & dosage / Q000494:pharmacology*
D006993:Hypnotics and Sedatives; D014991:Xylazine; D000075:Acepromazine; D008691:Methadone