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- Author or Editor: Cheryl Greenacre x
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Abstract
Objective—To evaluate the effect of IV administration of tramadol hydrochloride on the minimum alveolar concentration of isoflurane (ISOMAC) that prevented purposeful movement of rabbits in response to a noxious stimulus.
Animals—Six 6- to 12-month-old female New Zealand White rabbits.
Procedures—Anesthesia was induced and maintained with isoflurane in oxygen. A baseline ISOMAC was determined by clamping a pedal digit with sponge forceps until gross purposeful movement was detected or a period of 60 seconds elapsed. Subsequently, tramadol (4.4 mg/kg) was administered IV and the posttreatment ISOMAC (ISOMACT) was measured.
Results—Mean ± SD ISOMAC and ISOMACT values were 2.33 ± 0.13% and 2.12 ± 0.17%, respectively. The ISOMAC value decreased by 9 ± 4% after tramadol was administered. Plasma tramadol and its major metabolite (M1) concentrations at the time of ISOMACT determination varied widely (ranges, 181 to 636 ng/mL and 32 to 61 ng/mL, respectively). Intervals to determination of ISOMACT and plasma tramadol and M1 concentrations were not correlated with percentage change in the ISOMAC. Heart rate decreased significantly immediately after tramadol administration but by 10 minutes afterward was not different from the pretreatment value. Systolic arterial blood pressure decreased to approximately 60 mm Hg for approximately 5 minutes in 3 rabbits after tramadol administration. No adverse effects were detected.
Conclusions and Clinical Relevance—As administered, tramadol had a significant but clinically unimportant effect on the ISOMAC in rabbits. Higher doses of tramadol may provide clinically important reductions but may result in a greater degree of cardiovascular depression.
Abstract
Objective—To determine the pharmacokinetics of an orally administered dose of tramadol in domestic rabbits (Oryctolagus cuniculus).
Animals—6 healthy adult sexually intact female New Zealand White rabbits.
Procedures—Physical examinations and plasma biochemical analyses were performed to ensure rabbits were healthy prior to the experiment. Rabbits were anesthetized with isoflurane, and IV catheters were placed in a medial saphenous or jugular vein for collection of blood samples. One blood sample was collected before treatment with tramadol. Rabbits were allowed to recover from anesthesia a minimum of 1 hour before treatment. Then, tramadol (11 mg/kg, PO) was administered once, and blood samples were collected at various time points up to 360 minutes after administration. Blood samples were analyzed with high-performance liquid chromatography to determine plasma concentrations of tramadol and its major metabolite (O-desmethyltramadol).
Results—No adverse effects were detected after oral administration of tramadol to rabbits. Mean ± SD half-life of tramadol after administration was 145.4 ± 81.0 minutes; mean ± SD maximum plasma concentration was 135.3 ± 89.1 ng/mL.
Conclusions and Clinical Relevance—Although the dose of tramadol required to provide analgesia in rabbits is unknown, the dose administered in the study reported here did not reach a plasma concentration of tramadol or O-desmethyltramadol that would provide sufficient analgesia in humans for clinically acceptable periods. Many factors may influence absorption of orally administered tramadol in rabbits.
Abstract
OBJECTIVE
To perform a qualitative analysis of the distribution of µ- and κ-opioid receptor mRNA in the forebrain and midbrain of budgerigars (Melopsittacus undulatus).
SAMPLE
8 brains of male budgerigars.
PROCEDURES
Custom-made RNA hybridization probes (RNAscope; Advanced Cell Diagnostics Inc) were used for fluorescent in situ hybridization (FISH) assays performed on selected fresh frozen prepared sections of brain tissue to identify µ- and κ-opioid receptor mRNA.
RESULTS
There was κ-opioid receptor mRNA present in the nucleus dorsomedialis posterior thalami, lateral striatum, mesopallium, tractus corticohabenularis et corticoseptalis, griseum et fibrosum, stratum griseum centrale, medial striatum, and area parahippocampalis. There was µ-opioid receptor mRNA present in the stratum griseum centrale, stratum opticum, dorsomedialis posterior thalami, area parahippocampalis, medial striatum, and nidopallium intermedium.
CLINICAL RELEVANCE
Consistent with previous studies in pigeons and domestic chicks, κ-opioid receptors were more abundant than µ-opioid receptors in the samples of the present study. The results of this study may also help explain the hyperexcitability or lack of response that can occur with administration of pure µ-opioid receptor agonists, but not κ-opioid receptor agonists. This study was not quantitative, so further research should endeavor to compare the various regions of the brain using FISH technology.
Abstract
Objective—To validate a novel high-sensitivity radioimmunoassay (RIA) procedure developed to accurately measure the relatively low serum total thyroxine (T4) concentrations of birds and reptiles and to establish initial reference ranges for T4 concentration in selected species of psittacine birds and snakes.
Animals—56 healthy nonmolting adult psittacine birds representing 6 species and 42 captive snakes representing 4 species.
Procedure—A solid-phase RIA designed to measure free T4 concentrations in dialysates of human serum samples was used without dialysis to evaluate total T4 concentration in treated samples obtained from birds and reptiles. Serum T4 binding components were removed to allow assay of undialyzed samples. Assay validation was assessed by determining recovery of expected amounts of T4 in treated samples that were serially diluted or to which T4 was added. Intra- and interassay coefficient of variation (CV) was determined.
Results—Mean recovery of T4 added at 4 concentrations ranged from 84.9 to 115.0% and 95.8 to 119.4% in snakes and birds, respectively. Intra- and interassay CV was 3.8 and 11.3%, respectively. Serum total T4 concentrations for 5 species of birds ranged from 2.02 to 7.68 nmol/L but ranged from 3.17 to 142 nmol/L for blue-fronted Amazon parrots; concentrations ranged from 0.21 to 6.06 nmol/L for the 4 species of snakes.
Conclusions and Clinical Relevance—This new RIA method provides a commercially available, accurate, and sensitive method for measurement of the relatively low serum T4 concentrations of birds and snakes. Initial ranges for the species evaluated were established. (Am J Vet Res 2001;62:1750–1767)
Abstract
Objective—To determine the incidence of adverse events in ferrets vaccinated with a modified-live avian cell culture canine distemper virus vaccine licensed for use in ferrets, an inactivated rabies vaccine licensed for use in ferrets, or both.
Design—Retrospective study.
Animals—143 ferrets.
Procedure—Medical records were reviewed to identify ferrets that had an adverse event after vaccination.
Results—Adverse events developed within 25 minutes after vaccination in 13 ferrets. One ferret developed an adverse event after receiving a distemper and a rabies vaccine simultaneously and developed a second adverse event the following year after receiving the rabies vaccine alone. Therefore, a total of 14 adverse events were identified. All adverse events were an anaphylactic reaction characterized by generalized hyperemia, hypersalivation, and vomiting. Ten of the 14 anaphylactic reactions occurred after ferrets received both vaccines, 3 occurred after ferrets received the distemper vaccine alone, and 1 occurred after a ferret received the rabies vaccine alone. Incidences of adverse events after administration of both vaccines, the distemper vaccine alone, and the rabies vaccine alone were 5.6, 5.9, and 5.6%, respectively. Ferrets that had an anaphylactic reaction were significantly older at the time of vaccination than were ferrets that did not.
Conclusions and Clinical Relevance—Results suggest that there may be a high incidence of anaphylactic reactions after vaccination of domestic ferrets. Ferrets should be observed for at least 25 minutes after vaccination, and veterinarians who vaccinate ferrets should be prepared to treat anaphylactic reactions. (J Am Vet Med Assoc 2003;223:663–665)
Abstract
Objective—To describe morbidity, function, outcome, and owner satisfaction associated with limb amputation in domestic rabbits.
Design—Retrospective case series.
Animals—34 client-owned domestic rabbits.
Procedures—Medical records of domestic rabbits undergoing limb amputation for any cause between 2000 and 2009 were reviewed. The Kaplan-Meier method was used to estimate survival rate and median survival time, and variables were analyzed for relationship to risk of morbidity resulting in euthanasia and to outcome (survival vs nonsurvival [death or euthanasia]). Owners were interviewed to determine satisfaction with outcome of the procedure.
Results—28 rabbits underwent pelvic limb amputation, and 6 underwent thoracic limb amputation. At the last follow-up, 18 rabbits were dead, 9 were alive, and 7 were lost to follow-up. Median overall survival time was 720 days (range, 4 to 3,250 days). Acute and delayed or chronic complications were observed in 22 of 34 and 19 of 32 rabbits, respectively, most commonly difficulty ambulating, hygiene issues, and pododermatitis (cutaneous ulcers at the hock). Six rabbits were euthanized because of complications at a median of 104 days (range, 4 to 399 days) after surgery. Risk of morbidity resulting in euthanasia increased with heavier body weight and concurrent disease affecting ambulation at the time of amputation. Weight, age, and pododermatitis at the time of amputation were significantly negatively associated with survival time. Thirty-one (91%) owners were satisfied with the outcome.
Conclusions and Clinical Relevance—Although limb amputation was tolerated by most rabbits and most owners were satisfied, complications resulted in death in 6 of 34 (18%) rabbits, and 19 of 32 (59%) developed chronic complications. Amputation in heavy rabbits or those with concurrent pododermatitis, musculoskeletal disease, or neurologic disease should be considered carefully. Because of the small sample size and retrospective nature of this study, results should be interpreted as exploratory and hypothesis generating.