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Buprenorphine: it’s not all static in rabbits

Influence of a single dose of buprenorphine on rabbit (Oryctolagus cuniculus) gastrointestinal motility.
Deflers H et al (2018). Veterinary Anaesthesia and Analgesia 45 510-519  

What did this study find?

Buprenorphine, a partial agonist opioid, is not licenced for administration to rabbits but it is commonly used in this species at doses ranging from 20 - 100µg/kg.1 In this study there was no significant difference between time to presence of faeces in the pelvic area with or without high dose buprenorphine administration (100µg/kg IM). Thus, a single dose of buprenorphine does not appear to slow rabbit intestinal transit time. 


In rabbits the use opioids have often been restricted due to the potential for gastrointestinal (GI) side effects, including ileus.  To date there have been few significant studies specifically examining the gastrointestinal side effects of buprenorphine in this species.  This study hypothesized that buprenorphine would slow GI transit time.  Additionally, no known studies have been published assessing the use of non-invasive techniques to determine rabbit gastrointestinal transit time.

The aim of this study was therefore two-fold:  

  1. To establish a novel and non-invasive imaging protocol for the assessment of rabbit digestive transit
  2. To determine the effects of a single, high dose of buprenorphine on intestinal transit time and gut motility in healthy young male rabbits. 

Study design

Fifteen 3 month old, specific pathogen-free, male New Zealand White rabbits weighing 2.68 ± 0.28 kg were acclimatised in groups of 5 for 7 days.  They had ad libitum access to hay, water and commercial rabbit feed and were handled regularly.

Radiographic and ultrasound examinations were performed twice: During week 1 (no treatment) and again during week 2 following a single dose of 100µg/kg intramuscular buprenorphine.  Imaging was performed at 0, 15, 30 and 6 minutes, then 3, 6, 12 and 24 hours in both the no treatment and treatment groups, with observations starting 5 minutes after buprenorphine administration in the treatment group.  All imaging examinations were completed by the same experienced radiologist who was blinded to the treatment group.  All animals received no treatment and buprenorphine.

Radiographic examinations were performed following a barium meal prepared with standard food concentrate, barium and water.  The aim of mixing the barium with food was to maintain gastrointestinal activity as close to normal as possible. Observations of the stomach and caecum were made and a barium retention score of 0 (no barium) to 3 (large amount of barium) assigned.  Transit time was estimated based on the apparition time of faeces in the pelvic area.

During ultrasound examination pyloric and duodenal contractions were counted during a 2 minute period for each ultrasound series. A contraction was defined as a reduction of the lumen diameter of at least 50%.

Ultrasonography and radiography were chosen to minimise stress and contrast strongly with the traditional, more invasive, methods used to study digestive transit in the rabbit.  


In this study, buprenorphine administration, at a dose of 100µg/kg intramuscularly, decreased the barium retention score in the stomach but had no effect on the barium retention score in the caecum. Buprenorphine had no effect on the time for faeces to appear in the pelvic area when compared to untreated rabbits.

Duodenal contractions occurred in groups of about 12, and at a higher rate than the distinct, isolated, pyloric contractions.  These observations were similar in both the treated and untreated groups. There was an increase in the rate of pyloric and duodenal contractions following buprenorphine administration, although there did appear to be fewer dynamic pyloric contractions in the treatment group (subjective data). 

No rabbit struggled during the study, and all animals ate and drank normally throughout. 

Why is this important?

Buprenorphine is a partial agonist opioid frequently administered for mild to moderate pain.  Although it is not licenced for rabbits, it is commonly used in general practice at doses ranging from 20 - 100µg/kg.1 However, Veterinary Practitioners treating rabbits often finds themselves in a dilemma: Pain can play a significant role in the establishment of ileus in the rabbit; but opioid analgesics are commonly restricted due to fear of drug itself inducing ileus.  In a non-invasive manner, this rabbit study examined the gastrointestinal effects of a high, intramuscular, dose of buprenorphine.

The results demonstrated there was no significant difference between time to presence of faeces in the pelvic area with and without buprenorphine administration. Thus, a single high dose of buprenorphine (100µg/kg) appears to have no adverse effect on gastrointestinal motility in healthy rabbits.  

Article by
Dr. Karen Heskin

Veterinary Technical Manager, Jurox UK

Originally published: Thursday, 13th September 2018


  1. Fiorello CV & Divers SJ (2013). Rabbits. Exotics Animal Formulary (4th edition). Elsevier.  517-559

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