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Safety studies of post-surgical buprenorphine therapy for mice
Karl A Traul1, Jennell B Romero2, Cory Brayton2
1Pharmaceutical Consulting, Lawrenceville, NJ, USA.
Abstract:
The use of appropriate analgesia in laboratory mice may be suboptimal because of concerns about adverse events (AE). Target Animal Safety trials were conducted to determine the safety of an extended-release suspension of buprenorphine. Drug or control suspensions were injected subcutaneously in surgically-treated BALB/c mice anesthetized with ketamine-xylazine to mimic post-operative conditions in which the compound might commonly be administered. Single and repeat five-fold (5×) excesses of the 3.25 mg/kg intended dose were used to provoke potential AE. Trials included prospective measurements of weight changes, blood chemistry, hematology, and histopathology. Clinical and histopathology findings were similar in drug-treated and control mice in a four-day trial using a single 16.25 mg/kg, 5× overdose of the drug. In a 12-day trial, which used a total buprenorphine dose of 48.75 mg/kg, clinical and histopathology values were also similar in control and drug-treated female mice. In the male arm of the repeat-overdose trial, two of eight mice died on the morning of day 12, three days following the third 16.25 mg/kg overdose administration. Histopathology did not reveal a cause of death. In a 14-month trial using a single 3.25 mg/kg dose of the drug, no significant findings identified potential AE. These findings indicate a high tolerance to an extended-release buprenorphine suspension administered post-operatively in mice with appropriate husbandry.
Insights
Extended-release buprenorphine shows high tolerance in laboratory mice, even at high doses. These safety trials indicate it is a viable option for post-operative pain management in mice.
Area of Science:
- Veterinary pharmacology
- Laboratory animal science
Background:
- Concerns regarding adverse events (AE) may lead to suboptimal analgesia in laboratory mice.
- Buprenorphine is a commonly used analgesic, but its safety profile in mice, particularly extended-release formulations, requires thorough investigation.
Purpose of the Study:
- To evaluate the safety and identify potential adverse events (AE) of an extended-release buprenorphine suspension in laboratory mice.
- To determine the maximum tolerated dose and assess the safety of repeated administration in a post-operative setting.
Main Methods:
- Target Animal Safety trials were conducted using BALB/c mice mimicking post-operative conditions.
- Mice received subcutaneous injections of buprenorphine or control suspensions at the intended dose (3.25 mg/kg) and five-fold (5×) excesses (16.25 mg/kg).
- Evaluations included prospective measurements of weight changes, blood chemistry, hematology, and histopathology over various trial durations (4 days, 12 days, 14 months).
Main Results:
- No significant clinical or histopathological findings were observed in mice receiving a single 5× overdose (16.25 mg/kg) over four days.
- In a 12-day repeat-dose study, female mice showed similar clinical and histopathology results between control and buprenorphine groups (total dose 48.75 mg/kg).
- In male mice during the repeat-overdose trial, two out of eight died following the third 16.25 mg/kg overdose, with no cause identified via histopathology. A 14-month study with a single 3.25 mg/kg dose revealed no significant adverse findings.
Conclusions:
- Extended-release buprenorphine suspension demonstrates a high safety tolerance in laboratory mice under appropriate husbandry conditions.
- The findings support the use of this formulation for post-operative analgesia in mice, with careful monitoring recommended during high-dose or repeated administrations.
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