Abstract
Objective
To measure plasma methadone concentrations in bitches and the umbilical cords of their
puppies after systemic or epidural administration.
Study design
Prospective, randomized, clinical study.
Animals
A total of 27 healthy pregnant female dogs undergoing caesarean section, 4.3 ± 2.3
years of age and weighing 19.9 ± 13.2 kg.
Methods
The dogs were randomly divided into three groups: 1) intramuscular methadone (0.3
mg kg–1) (group MET; n = 9); 2) epidural methadone (0.1 mg kg–1) (group METEPI; n = 9); and 3) epidural lidocaine (4.4 mg kg–1) [group CON (control group); n = 9]. Ten minutes before induction, methadone was administered intramuscularly to
the group MET dogs. Anaesthesia was induced with propofol and maintained with isoflurane.
Cardiovascular and respiratory parameters were monitored throughout the anaesthesia.
After induction, epidural anaesthesia was administered to dogs in groups METEPI and
CON. Before any treatment (T0) and, as soon as the last foetus was removed from the
uterus (T1), venous blood samples were collected from each dog into heparinized tubes;
the umbilical cords were collected and stored at –80 °C until pharmacological analysis
was carried out. The samples were analysed using ultra performance liquid chromatography.
Results
The cardiorespiratory parameters of the bitches and of the puppies at birth, and the
Apgar scores did not differ significantly between groups. At T1 both the median maternal
methadone plasma concentration and the median methadone umbilical cord concentration
were higher in group MET compared to group METEPI (p = 0.0018 and p = 0.004, respectively). The maternal plasma concentration was higher than the concentration
in the umbilical cords (p = 0.05) in group METEPI but not in group MET (p = 0.25).
Conclusions and clinical relevance
Epidural methadone (0.1 mg kg–1) administered to bitches undergoing caesarean section is associated with lower umbilical
cord methadone concentrations as compared with intramuscularly administered methadone
at higher dosages (0.3 mg kg–1).
Keywords
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Article info
Publication history
Published online: November 10, 2018
Accepted:
October 26,
2018
Received:
February 21,
2018
Identification
Copyright
© 2018 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.
