Use of subcutaneous maropitant at two dosages for pain management in domestic rabbits (Oryctolagus cuniculus) undergoing elective ovariohysterectomy or orchiectomy

OBJECTIVE

To describe the effect of two doses of maropitant on pain scores, food intake, and fecal output in domestic rabbits (Oryctolagus cuniculus) undergoing elective ovariohysterectomy or orchiectomy.

ANIMALS

26 (11 female, 15 male) rabbits from three institutions.

PROCEDURES

Rabbits were randomly assigned to one of three treatment groups: low-dose maropitant (LDM; 2 mg/kg SC once; n=8), moderate-dose maropitant (MDM; 4 mg/kg SC once; n=10), and control (saline equivalent to 4 mg/kg maropitant SC once; n=8), administered prior to surgery. Following surgery, all rabbits were provided buprenorphine (0.06 mg/kg q 8 hours) and meloxicam (1 mg/kg q 24 hours) intramuscularly. Rabbits were monitored using video surveillance postoperatively until 24 hours after surgery or discharge from the hospital, whichever came first. Pain scores were assessed by three blinded observers, and results were grouped into early (0-4 hours), mid (5-8 hours), and late (12-24 hours) time frames. Food intake and fecal output were compared between groups. Statistical analysis was performed using Chi square, Fisher's exact tests, and a mixed model approach.

RESULTS

There were no adverse effects with maropitant administration. Rabbits that received MDM had significantly lower pain scores in the mid-time frame and behavior scores in the late-time frame compared to controls. Male rabbits consumed more food than females and rabbits hospitalized longer than 12 hours consumed more food than those that were discharged prior. No significant differences were detected in facial grimace scale scores, food intake, or fecal production among treatment groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Moderate dose maropitant decreased pain related behaviors in the mid-time frame and behavior scores in the late-time frame after surgery. Further studies are necessary to better characterize the potential use of maropitant in postoperative analgesia.

Comparison between Carprofen and Meloxicam for Post-Neutering Pain Management in Pet Rabbits

Surgical neutering in pet rabbits is common practice to prevent reproduction and associated health issues. Adequate postoperative pain management is crucial for recovery, yet effective methods in clinical settings remain underexplored. This study compared the analgesic effects of carprofen and meloxicam in pet rabbits undergoing surgical neutering. Fifty rabbits of varied demographics were included, with pain assessed using the Centro Animali Non Convenzionali Rabbit Scale (CANCRS). Rabbits were allocated to receive postoperative 2 mg kg-1 carprofen or 1 mg kg-1 meloxicam by subcutaneous injection. Anesthesia was induced with an intramuscular combination of ketamine (20 mg kg-1), medetomidine (0.4 mg kg-1), and butorphanol (0.2 mg kg-1), and ovariectomy or orchiectomy were performed. The CANCRS scale was used to assess pain by evaluating the rabbit preoperatively, 6 h postoperatively, and at three time points the following day. Times of return to spontaneous feeding and fecal production were also recorded. No statistically significant difference was found between treatment groups based on CANCRS scores and resumption of food intake and fecal output. No clinically detectable adverse effects were noted. While limitations include the use of a single pain assessment scale and the absence of a placebo control group, the results suggest that both carprofen and meloxicam can be viable options in clinical practice. Further research utilizing diverse pain assessment methods is warranted to enhance understanding and optimize pain management strategies for rabbits undergoing surgical procedures.

Measurement of Cyclooxygenase Products in Plasma as Markers for Inhibition of Cyclooxygenase Isoforms by Oral Meloxicam in New Zealand White Rabbits (Oryctolagus cuniculus )

Pain management in rabbits is a challenging task that is complicated by the rabbit's ability to hide signs of distress and the limited pharmacologic data available for this species. Pharmacokinetic data has shown that in rabbits, meloxicam, a nonsteroidal anti-inflammatory NSAID, reaches plasma concentrations that are known to provide analgesia in dogs and cats; these concentrations could theoretically alleviate pain in rabbits. However, the inhibitory effects of meloxicam on cyclooxygenase (COX) isoforms have not been studied in rabbits. In this study, we measured the products of COX-1 and COX-2 after the oral administration of a single 1 mg/kg dose of meloxicam to New Zealand White rabbits (n = 6). Blood samples were collected before drug administration (T0) and then at predetermined time points over 48 h. Plasma prostaglandin E₂ (PGE₂ ) and thromboxane (TxB₂) concentrations were measured as surrogate markers for COX-1 and COX-2, respectively, by using commercial ELISA kits. After meloxicam administration, both TxB₂ and PGE₂ plasma concentrations fell significantly below baseline, with maximal mean reductions to 80% and 60% of baseline at 8 h, respectively. The reduction in PGE₂ concentrations was followed by a significant increase that moved its mean plasma concentrations toward baseline between 8 and 24 h. Adverse effects such as lethargy, inappetence, or changes in fecal production were not observed in any rabbits. In conclusion, meloxicam appeared to significantly inhibit both COX-1 and COX-2 with a time course similar to previously reported meloxicam plasma concentration-time profiles in rabbits. Our data suggest that a dosage of 1 mg/kg given orally could provide analgesia to rabbits, but a more frequent dosing interval than the currently recommended daily dosing may be required to maintain clinical efficacy.

Examination of the pharmacokinetics and differential inhibition of cyclooxygenase isoenzymes in New Zealand white rabbits (Oryctolagus cuniculus) by the Non-Steroidal anti-inflammatory Robenacoxib

Effective rabbit analgesia is challenging, and there are few studies available on the newer COX-2 selective NSAIDs, such as robenacoxib. This study aimed to establish the pharmacokinetics of oral and subcutaneous robenacoxib, describe its inhibitory actions on COX enzymes, and develop dosing, using six healthy New Zealand white rabbits. Pharmacokinetics were determined from plasma concentrations after oral administration of robenacoxib (0.83-0.96 mg/kg) and also after subcutaneous administration (2 mg/kg). The inhibitory actions of robenacoxib were evaluated by measuring plasma concentrations of thromboxane B₂ (TBX₂ ) and prostaglandin E₂ (PGE₂ ) as surrogate markers of cyclooxygenase enzyme isoform inhibition. The mean maximum concentration for oral and subcutaneous administration was 0.23 μg/ml and 5.82 μg/ml, respectively. Oral robenacoxib administration did not demonstrate a significant difference between any time point for PGE₂ or TBX₂ , though subcutaneous administration did for both. There was no significant difference in PGE₂ or TBX₂ concentrations at any time point when comparing subcutaneous versus oral routes. Although the results support that plasma robenacoxib exceeds the therapeutic levels compared to dogs and cats, there was little significance in the difference in the changes associated with COX-1 and COX-2 inhibition. Further studies are warranted to determine appropriate dosing, safety, and efficacy in rabbits.

Treatment of Pain in Rabbits

Rabbits occupy facets of veterinary medicine spanning from companion mammals, wildlife medicine, zoologic species, and research models. Therefore, analgesia is required for a variety of conditions in rabbits and is a critical component of patient care. Considerations when selecting an analgesic protocol in rabbits include timing of administration, route of administration, degree or anticipated pain, ability to access or use controlled drugs, systemic health, and any potential side effects. This review focuses on pharmacologic and locoregional management of pain in rabbits and emphasizes the need for further studies on pain management in this species.

Changes in rabbit lymphocyte subpopulations and activation following long-term administration of meloxicam

Meloxicam is a commonly used analgesic in rabbits. However, its possible impact on lymphocyte subpopulations remained unknown. The aim of the study was to investigate a possible effect of long-term administration of meloxicam on rabbit lymphocyte subpopulations. The study included 8 rabbits given meloxicam orally once daily (1 mg/kg BW) for 14 days and 8 rabbits as a control group. Peripheral blood samples were collected on day 0 (before the first dose of meloxicam), day 3, 7 and 14. Samples were evaluated with a haematology analyser and a flow cytometer. A significant decrease in T: B cell ratio was found in all samples taken during meloxicam administration compared to day 0, as well as in comparison with the control group (P < 0.01). A significant increase (P < 0.05) in proportion of CD5 +CD8 + lymphocytes occurred by day 3. Subsequently, although the values slightly decreased, they still remained elevated throughout all the experiment compared to the values from day 0 (P < 0.05). A slight decrease in T and B cell activation (CD5 +CD25 + and IgM+CD25 +) noticed by day 3, declined during the next days of administration and became more and more significant (finally, P = 0.0078). Since a high significant decrease (P < 0.01) in both T and B cell activation as well as a significant increase (P < 0.05) in CD5 +CD8 + T cells proportion were observed after meloxicam administration, a predicted effect of long-term administration of meloxicam on rabbit lymphocytes was confirmed.

Abnormal Repetitive Behaviors and Self-Mutilations in Small Mammals

Self-mutilation and abnormal repetitive behaviors in small mammals are challenging conditions for veterinary practitioners. The etiology may be difficult to identify, and the treatment is often unrewarding unless the specific underlying cause can be found. Reinforcement of the abnormal behavior may also complicate the treatment. However, medical causes, including painful conditions, should be investigated thoroughly. Owing to the small blood volume of many small exotic mammals and the associated risk of hypovolemia in case of hemorrhage, an hospitalization with potent multimodal analgesia and physical barriers to prevent self-mutilation is often warranted. Psychogenic drugs may be useful in some cases.

Analgesia in pet rabbits: a survey study on how pain is assessed and ameliorated by veterinary surgeons

BACKGROUND

In the last 20 years, two studies on the veterinary use of perioperative analgesia in small mammals reported a limited use of analgesics in rabbits but suggested an increasing use over the years. The aim of this study was to better understand how pain is treated and ameliorated in rabbits while under veterinary care.

METHODS

An online survey of 60 questions was developed and advertised at national and international veterinary conferences, in veterinary publications and on social media.

RESULTS

In total 94.3 per cent of the respondents routinely administered nonsteroidal anti-inflammatory drugs (NSAIDs) to rabbits undergoing surgical procedures such as neutering, 71.4 per cent administered an opioid and 70.3 per cent routinely administered multimodal analgesia, although dosages do not always match current consensus opinion. Buprenorphine and meloxicam were the most common analgesic drugs prescribed by the respondents. The dosage of meloxicam administered both parenterally and orally varied widely.

CONCLUSION

Rabbit analgesia has improved over recent years similarly to the trend seen in other companion animals. However, overall it seems that pain assessment is still limited in rabbits. The lack of multimodal composite pain scales specific for rabbits makes this task even more challenging.

Pharmacokinetics and absolute oral bioavailability of meloxicam in guinea pigs (Cavia porcellus)

OBJECTIVE

To investigate the pharmacokinetics and absolute oral bioavailability of meloxicam in guinea pigs.

STUDY DESIGN

Prospective crossover study.

ANIMALS

A group of six healthy male Dunkin Hartley guinea pigs.

METHODS

A single dose of meloxicam (1.5 mg kg^-1) was administered orally and intravenously (IV) to six healthy male guinea pigs. A wash-out period of 48 hours was taken into account between administrations (oral and IV) in the same animal. Blood was sampled through a central venous catheter before administration (t = 0 hours) and at 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 16, 20, 24 and 28 hours post administration. After centrifugation, plasma concentrations of meloxicam were measured by high-performance liquid chromatography with UV detection, and pharmacokinetic parameters were calculated using noncompartmental analysis.

RESULTS

Meloxicam in guinea pigs exhibited a moderate absorption rate after oral dosing (time to maximal plasma concentration 3.7 ± 1.7 hours) and maximal plasma concentration was 0.92 ± 0.30 μg mL^-1. After IV administration, total body clearance and volume of distribution were 0.13 ± 0.04 and 0.72 ± 0.36 L kg^-1, respectively. Terminal half-life was 3.7 ± 0.7 hours and 3.5 ± 1.1 hours after IV and oral administration, respectively. Body extraction ratio was 0.0087 and mean absorption time was 3.8 ± 1.7 hours. The absolute oral bioavailability was 0.54 ± 0.14 in unfasted guinea pigs.

CONCLUSIONS AND CLINICAL RELEVANCE

This study reported the pharmacokinetics of meloxicam in guinea pigs. Studies concerning efficacy and safety are the next step towards a rational use of this drug in guinea pigs.

Pain and analgesia in pet rabbits within the veterinary environment: a review

OBJECTIVE

To provide an overview of pain and analgesia in rabbits with the aim of developing a more accurate understanding of these topics. To illustrate and discuss the areas that have advanced in recent years and those that still require further research.

DATABASES USED

Three key subject resources were used: Web of Science, Medline and CAB Abstracts. Search terms were rabbits, lagomorphs, laboratory animals, pet, pain, surgical procedures, ovariohysterectomy, orchiectomy, castration, analgesia, opioids, and non-steroidal anti-inflammatory drugs. References from books and articles relevant to the topics were also included.

CONCLUSIONS

Rabbit medicine has improved over the last 20 years, but the literature suggests that pain management in this species is still inadequate and veterinary professionals believe their knowledge of pain and analgesia in this species is limited. Assessment and quantification of pain in rabbits can be challenging in a clinical environment not only because, as a prey species, rabbits tend to hide signs of pain but also because there are no validated methods to assess pain, except the Rabbit Grimace Scale, which is based on only one rabbit breed. Current consensus is that perioperative multimodal analgesia is the best practice. However, it is not widely used in rabbits. In rabbits, analgesia protocols and dosages reported in the literature are often poorly researched and do not result in complete pain amelioration with the return of normal. The present literature on rabbit pain and analgesia presents gaps either due to unexplored areas or insufficient findings. Further research should focus on these areas with the aim of improving the welfare of rabbits within a veterinary clinic.

PHARMACOKINETICS OF MELOXICAM FOLLOWING A SINGLE ORAL DOSE IN MALAYAN FLYING FOXES ( PTEROPUS VAMPYRUS)

  Meloxicam, a COX-2 selective nonsteroidal anti-inflammatory medication, has been used in many exotic animals at doses extrapolated from domestic animal pharmacokinetic and pharmacodynamic studies. Increasing evidence suggests that significant species differences exist in meloxicam metabolism. Because of this, dose extrapolation from domestic animals may not be appropriate for exotic species. The objective of this study was to investigate the pharmacokinetics of meloxicam in a population of male Malayan flying foxes, Pteropus vampyrus, following a single oral dose of 0.2 mg/kg. Using a sparse sampling method based on a pilot study, two blood samples from each of 10 bats were collected over an 8-hr time period. Analysis of meloxicam in plasma samples was conducted using reversed-phase high-performance liquid chromatography. The peak plasma concentration of 598 ± 157.5 ng/ml occurred at 1.0 hr post dosing. The terminal half-life was 1.1 ± 0.1 hr, which indicates that meloxicam is rapidly metabolized in this species. No adverse clinical effects were noted during the study period. A single oral dose of 0.2 mg/kg appears safe for use in male Malayan flying foxes, but due to rapid elimination, frequent dosing may be required to maintain plasma concentrations within a therapeutic range. Multidose studies are needed to determine if plasma accumulation of meloxicam occurs.

Advancements in Evidence-Based Analgesia in Exotic Animals

The importance of appropriate recognition, assessment, and treatment of pain in all veterinary species, including exotic animals, cannot be overstated. Although the assessment of pain perception in nondomestic species is still in its infancy, this does not preclude appropriate analgesic management in these species. Although analgesic drug selection is often based on data extrapolated from similar species, as the pharmacokinetics and pharmacodynamics of many drugs can vary greatly between species, an evidence-based approach to analgesic therapy should be used whenever possible. This article provides an overview of recent advances in evidence-based analgesic management in companion exotic animals.