(1) Objective: To investigate the
analgesic effects of intravenous
acetaminophen after
intravenous administration in dogs presenting for ovariohysterectomy. (2) Methods: 14 ASA I client-owned female entire dogs. In this randomized, blinded, clinical study, dogs were given
meperidine and
acepromazine intramuscularly before induction of
anesthesia with intravenous
propofol.
Anesthesia was maintained with
isoflurane in
oxygen. Intravenous
acetaminophen 20 mg/kg or
0.9% NaCl was administered postoperatively.
Pain assessments were conducted using the Glasgow
Pain Scale short form before
premedication and
at 10, 20, 60, 120, and 180 min post-extubation or until rescue
analgesia was given. The
pain scores, times, and incidences of rescue
analgesia between the groups was compared. Blood was collected before and 2, 5, 10, 20, 40, and 80 min after
acetaminophen administration.
Acetaminophen plasma concentration was quantified by liquid chromatography-mass spectrometry. The
acetaminophen plasma concentration at the time of each
pain score evaluation was subsequently calculated. (3) Results: There was no significant difference in
pain scores
at 10 min, highest
pain scores, or time of rescue
analgesia between groups. In each group, 3 dogs (43%) received rescue
analgesia within 20 min. (4) Conclusions: Following ovariohysterectomy in dogs, there was no detectable
analgesic effect of a 20 mg/kg dosage of intravenous
acetaminophen administered at the end of surgery.