Antinociceptive effects after oral administration of tramadol hydrochloride in Hispaniolan Amazon parrots (Amazona ventralis)

Evaluation of Thermal Antinociceptive Effects of Intramuscular Hydromorphone Hydrochloride in Great Horned Owls (Bubo virginianus)

Across the Americas, great horned owls (Bubo virginianus) are often presented to veterinarians for conditions requiring pain management. Although recent studies have evaluated opioid drugs in raptor species, information in Strigiformes is lacking. The objective of this study was to evaluate the analgesic effect and duration of action of hydromorphone hydrochloride, a full µ-opioid receptor agonist, in great horned owls. In a randomized, blinded, balanced crossover study, 6 adult birds (5 females and 1 male) received hydromorphone (0.3 and 0.6 mg/kg) or saline (0.9% NaCl) solution (0.03 mL/kg; control) in the left pectoral muscle, with a 7-day washout interval between treatments. Each bird was assigned an agitation-sedation score, and the thermal foot withdrawal threshold (TFWT) was measured at predetermined times before (t = 0 hours) and after treatment administration (t = 0.5, 1.5, 3, and 6 hours). Measurements of the TFWT were obtained with a test box equipped with a thermal perch, which delivered a gradually increasing temperature 40-62°C (104-143.6°F) to the right plantar surface of the owl's foot. Compared with controls, hydromorphone at 0.3 mg/kg dose resulted in significantly higher mean TFWT at 0.5 hours (P < 0.001), 1.5 hours (P = 0.003), and 3 hours (P = 0.005), whereas the 0.6 mg/kg dose resulted in significantly higher mean TFWT from 0.5 hours (P = 0.035) to 1.5 hours (P = 0.001). Both hydromorphone doses were associated with a significant change in the agitation-sedation score (P = 0.001), consistent with mild to moderate sedation. Two owls were observed tremoring after administration of the 0.6 mg/kg dose, which was not noted after the 0.5-hour timepoint; no other adverse effects were identified. This study offers scientific evidence to support the use of a µ-opioid agonist in great horned owls for pain management. Pharmacokinetics and other pharmacodynamic studies of other pain models evaluating hydromorphone and other opioid drugs in this species are still needed.

Use of tramadol as analgesic alternative in Harris hawk (Parabuteo unicinctus)

BACKGROUND

The Harris hawk is a bird of prey susceptible to traumatic injuries because it is useful for several purposes such as conservancy, biological control and falconry. Once received in rehabilitation centres or specialized clinics, it is necessary to provide proper analgesia.

OBJECTIVES

The aim of this study is to demonstrate the analgesic efficacy of tramadol in Harris hawks (PISADOL 50 PiSA Agropecuaria, S.A. de C.V. Calle 1 Norte, Manzana 2-25 Parque Industrial Tula Atitalaquia, Hgo, México), by the assessment of nociceptive threshold.

METHODS

A total of 24 adult Harris hawks were selected from a rehabilitation centre. The birds were randomly divided into four groups: control (saline solution), 5.0, 15.0 and 30.0 mg/kg of intramuscular tramadol. Nociception was produced with electrical stimuli of 9 V, applied in propatagial skin at 1, 5, 10, 20, 30, 45, 60, 90, 120, 180, 240, 300 and 360 min, assessing the nociceptive threshold and sedative effects produced by each treatment.

RESULTS

No difference was observed between control and tramadol group 5 mg/kg. At 15 mg/kg, the pain threshold increased from 20 to 240 min, with minimal sedative effects. At 30 mg/kg, there was a marked increase in pain threshold from 10 to 300 min, and sedative effects like wing and head drooping for a period of 90 min.

CONCLUSIONS

Tramadol can be an analgesic alternative for Harris's hawks, as it decreases the response to painful stimuli in this species when administered by intramuscular route.

Treatment of Pain in Birds

This article provides an overview of the current understanding of evidence-based clinical analgesic use in birds. The field of avian analgesia has dramatically expanded during the last 20 years, affording more options for alleviating both acute and chronic pain. These options include opioids, nonsteroidal anti-inflammatory drugs, local anesthetics, and/or other drugs like gabapentin, amantadine, and cannabinoids, acting at different points in the nociceptive system thereby helping to provide greater pain relief while reducing the risk of adverse effects when combined.

A Critical Review of the Pharmacokinetics and Pharmacodynamics of Opioid Medications Used in Avian Patients

Opioid drugs are used to manage moderate to severe pain in mammals and avian species. In dosing opioids for a particular species, it is optimal to use dosing regimens based on pharmacokinetics or pharmacodynamics studies conducted in the same species as variability in the physiology among different species may result in differences in drug pharmacokinetics and pharmacodynamics. Unfortunately, dosing regimens are typically extrapolated from closely related avian species or even mammals, which is unideal. Therefore, this critical review aims to collate and evaluate the dosing regimens of selected opioids: tramadol, hydromorphone, buprenorphine, butorphanol, and fentanyl, in avian species and its related safety, efficacy and pharmacokinetic data. Our review found specific dosing regimens not described in the Exotic Animal Formulary for tramadol used in Indian Peafowl (Pavo cristatus), Muscovy Duck (Cairina moschata) and Hispaniolan Parrot (Amazona ventralis); hydromorphone used in Orange-winged Parrot (Amazona amazonica); buprenorphine used in Cockatiel (Nymphicus hollandicus), American Kestrel (Falco sparverius) and Grey Parrot (Psittacus erithacus); and butorphanol used in Hispaniolan Parrot (Amazona ventralis), Broiler Chicken and Indian Peafowl (Pavo cristatus). Cockatiel appeared to not experience analgesic effects for hydromorphone and buprenorphine, and American Kestrel exhibited sex-dependent responses to opioids. The selected opioids were observed to be generally safe, with adverse effects being dose-dependent.

Pilot Study of a Single Dose of Orally Administered Tapentadol Suspension in Hispaniolan Amazon Parrots (Amazona ventralis)

Tapentadol is an analgesic agent that acts as both a µ-opioid receptor agonist and a norepinephrine reuptake inhibitor. It is a common therapeutic agent in human medicine for management of acute and chronic pain, and it is currently being investigated for use in veterinary medicine. Tapentadol was evaluated in Hispaniolan Amazon parrots (Amazona ventralis) because there is only 1 other oral opioid-like analgesic agent, tramadol, which has been evaluated in an avian species. The effectiveness of tramadol after administration to a patient involves a complex physiologic metabolism and has been found to have variable pharmacokinetics between species. Because of the lack of active metabolites from tapentadol, less interspecific variation was expected. Seven Hispaniolan Amazon parrots were used to evaluate the pharmacokinetics of tapentadol after a single 30 mg/kg PO administration of a compounded 5 mg/mL tapentadol suspension. Blood samples were collected before (time 0) and 0.25, 0.5, 0.75, 1, 1.5, 3, and 6 hours after administration, following a balanced, incomplete-block design. Plasma tapentadol concentrations were measured by high-pressure liquid chromatography with mass spectrometry. Results revealed detectable plasma concentrations in only 2 of 7 birds (29%), and the bird with the highest plasma levels had a peak concentration (C_max) of 143 ng/mL and a half-life (T _1/2) of 24.8 minutes. The variable plasma concentrations and short half-life of this drug in Hispaniolan Amazon parrots suggests that this drug would be of limited clinical use in this species; however, it is possible that this drug will be more bioavailable in other avian species.

Evaluation of the thermal antinociceptive effects of hydromorphone hydrochloride after intramuscular administration to orange-winged Amazon parrots (Amazona amazonica)

OBJECTIVE

To evaluate the thermal antinociceptive effects of hydromorphone hydrochloride after IM administration to orange-winged Amazon parrots (Amazona amazonica).

ANIMALS

8 healthy adult parrots (4 males and 4 females).

PROCEDURES

In a randomized crossover study, each bird received hydromorphone (0.1, 1, and 2 mg/kg) and saline (0.9% NaCl) solution (1 mL/kg; control) IM, with a 7-day interval between treatments. Each bird was assigned an agitation-sedation score, and the thermal foot withdrawal threshold (TFWT) was measured at predetermined times before and after treatment administration. Adverse effects were also monitored. The TFWT, agitation-sedation score, and proportion of birds that developed adverse effects were compared among treatments over time.

RESULTS

Compared with the mean TFWT for the control treatment, the mean TFWT was significantly increased at 0.5, 1.5, and 3 hours and 1.5, 3, and 6 hours after administration of the 1- and 2-mg/kg hydromorphone doses, respectively. Significant agitation was observed at 0.5, 1.5, and 3 hours after administration of the 1 - and 2-mg/kg hydromorphone doses. Other adverse effects observed after administration of the 1- and 2-mg/kg doses included miosis, ataxia, and nausea-like behavior (opening the beak and moving the tongue back and forth).

CONCLUSIONS AND CLINICAL RELEVANCE

Although the 1- and 2-mg/kg hydromorphone doses appeared to have antinociceptive effects, they also caused agitation, signs of nausea, and ataxia. Further research is necessary to evaluate administration of lower doses of hydromorphone and other types of stimulation to better elucidate the analgesic and adverse effects of the drug in psittacine species.

Analgesic Efficacy of Tramadol Compared With Meloxicam in Ducks (Cairina moschata domestica) Evaluated by Ground-Reactive Forces

The purpose of this study was to determine the efficacy of tramadol and meloxicam in an induced, temporary arthritis model in ducks as assessed by ground-reactive forces measured by a pressure-sensitive walkway (PSW) system. Twelve ducks (Cairina moschata domestica) were randomly separated into 3 equal groups of 4 birds each: water control, tramadol treatment, and meloxicam treatment. Baseline measurements were collected by having all ducks walk along a 3-m-long PSW in a custom-built corral before anesthesia and induction of arthritis. Arthritis was induced in all groups through injection, under anesthesia, of a 3% monosodium urate (MSU) solution into the intertarsal joint. One hour after MSU injection, birds were orally gavage fed 1 mL of tap water (control), tramadol (30 mg/kg), or meloxicam (1 mg/kg). After treatments, all ducks were reevaluated on the PSW at 1, 2, 3, 4, 8, and 24 hours post-MSU injection. The difference in maximum force was significantly greater in the control group than in both the tramadol- (P = .006) and meloxicam-treated (P = .03) individuals. Post hoc comparisons revealed differences between control and treated birds occurred only at the 3- and 4-hour time points after administration. No differences were found in the absolute difference in maximum force between tramadol- and meloxicam-treated birds at any time point (P > .05). Results of this study support the hypothesis that tramadol (30 mg/kg PO) and meloxicam (1 mg/kg PO) improve certain objective variables in an induced arthritis model in ducks. Our findings also support studies in other avian species that determined that both tramadol and meloxicam are effective analgesic drugs in some birds.

Intercostal celiotomy for removal of proventriculus foreign body in muscovy duck (Cairina moschata): case report

ABSTRACT Ducks, geese and swans are included in the Anatidae family, Anseriformes order. The leading injuries causes to waterfowl are tangling in fishing materials and foreign bodies ingestion. A muscovy duck (Cairina moschata) was referred for treatment at Veterinary Teaching Hospital and a radiographic examination showed the presence of a hook in the coelom. Surgical exposure and incision of the proventriculus was made through left intercostal access and the hook along with a fishing line were gently removed. The animal began to feed voluntarily at the fourth post-operative day and two weeks after the procedure the patient was clinically well and was released to wild. This surgical approach differs in some aspects from the listed techniques in the known literature. It proved to be a viable and appropriate alternative to treat this affection since it did not cause any trans- or post-operative complications and enabled rapid recovery and subsequent patient release.

Influence of tramadol on anesthesia times, analgesia and electrocardiogram associated with injection anesthesia in common buzzards (Buteo buteo)

A balanced anesthesia protocol is called perfect when it has fast induction, excellent recovery, the least effect on the cardiopulmonary system and sufficient analgesia. Many of anesthetic combinations have an analgesic effect without opioids. However, at the end of anesthesia, analgesia decreases or is incomplete. The purpose of this study was to evaluate anesthesia times, electrocardiogram (ECG) and analgesic effect of tramadol when administrated with ketamine, ketamine-diazepam, ketamine-midazolam, and ketamine-xylazine and selected a balanced anesthesia protocol in buzzards. Ten adult common buzzards (Buteo buteo) received seven different anesthetic protocols (with or without tramadol). In each protocol, anesthesia times, electrocardiograph parameters and analgesic effect were recorded. Excluding ketamine-tramadol, all protocols produced deep anesthesia in all buzzards. Among of all protocols, no significant differences regarding the amplitude and duration of waves (P, QRS and T) was found. By adding tramadol to anesthetic protocols, response duration to thermal sense increased up 3 hr after recovery. Tramadol did not make considerable effects on anesthesia times and ECG and made analgesic effect up to 3 hr when used with ketamine-benzodiazpins or ketamine-xylazine. Therefore, tramadol can be used with injectable anesthetics to make suitably balanced anesthesia in buzzards.

Evaluation of the thermal antinociceptive effects and pharmacokinetics after intramuscular administration of buprenorphine hydrochloride to cockatiels (Nymphicus hollandicus)

OBJECTIVE To evaluate thermal antinociceptive effects and pharmacokinetics of buprenorphine hydrochloride after IM administration to cockatiels (Nymphicus hollandicus). ANIMALS 16 adult (≥ 2 years old) cockatiels (8 males and 8 females). PROCEDURES Buprenorphine hydrochloride (0.3 mg/mL) at each of 3 doses (0.6, 1.2, and 1.8 mg/kg) and saline (0.9% NaCl) solution (control treatment) were administered IM to birds in a randomized within-subject complete crossover study. Foot withdrawal response to a thermal stimulus was determined before (baseline) and 0.5, 1.5, 3, and 6 hours after treatment administration. Agitation-sedation scores were also determined. For the pharmacokinetic analysis, buprenorphine (0.6 mg/kg) was administered IM to 12 of the birds, and blood samples were collected at 9 time points ranging from 5 minutes to 9 hours after drug administration. Samples were analyzed with liquid chromatography-mass spectrometry. Pharmacokinetic parameters were calculated with commercial software. RESULTS Buprenorphine at 0.6, 1.2, and 1.8 mg/kg did not significantly change the thermal foot withdrawal response, compared with the response for the control treatment. No significant change in agitation-sedation scores was detected between all doses of buprenorphine and the control treatment. Plasma buprenorphine concentrations were > 1 ng/mL in all 4 birds evaluated at 9 hours. CONCLUSIONS AND CLINICAL RELEVANCE Buprenorphine at the doses evaluated did not significantly change the thermal nociceptive threshold for cockatiels or cause sedative or agitative effects. Additional studies with other pain assessments and drug doses are needed to evaluate the analgesic and adverse effects of buprenorphine in cockatiels and other avian species.

Pharmacokinetics of orally administered tramadol in Muscovy ducks (Cairina moschata domestica)

This study documents the pharmacokinetics of oral tramadol in Muscovy ducks. Six ducks received a single 30 mg/kg dose of tramadol, orally by stomach tube, with blood collection prior to and up to 24 hr after tramadol administration. Plasma tramadol, and metabolites O-desmethyltramadol (M1), and N,O-didesmethyltramadol (M5) concentrations were determined by high-pressure liquid chromatography (HPLC) with fluorescence (FL) detection. Pharmacokinetic parameters were calculated using a one-compartment model with first-order input. No adverse effects were noted after oral administration. All ducks achieved plasma concentrations of tramadol above 0.10 μg/ml and maintained those concentrations for at least 12 hr. Elimination half-life was 3.95 hr for tramadol in ducks, which is similar to other avian species. All ducks in this study produced the M1 metabolite and maintained plasma concentrations above 0.1 μg/ml for at least 24 hr.

Evaluation of the thermal antinociceptive effects and pharmacokinetics of hydromorphone hydrochloride after intramuscular administration to cockatiels (Nymphicus hollandicus)

OBJECTIVE To evaluate the thermal antinociceptive effects and pharmacokinetics of hydromorphone hydrochloride after IM administration to cockatiels (Nymphicus hollandicus). ANIMALS 16 healthy adult cockatiels. PROCEDURES During the first of 2 study phases, each cockatiel received each of 4 treatments (hydromorphone at doses of 0.1, 0.3, and 0.6 mg/kg and saline [0.9% NaCl] solution [0.33 mL/kg; control], IM), with a 14-day interval between treatments. For each bird, foot withdrawal to a thermal stimulus was determined following assignment of an agitation-sedation score at predetermined times before and for 6 hours after each treatment. During the second phase, a subset of 12 birds received hydromorphone (0.6 mg/kg, IM), and blood samples were collected at predetermined times for 9 hours after drug administration. Plasma hydromorphone concentration was determined by liquid chromatography-mass spectrometry. Noncompartmental analysis of sparse data was used to calculate pharmacokinetic parameters. RESULTS Thermal withdrawal response did not differ among the 4 treatment groups at any time. Agitation-sedation scores following administration of the 0.3-and 0.6-mg/kg doses of hydromorphone differed significantly from those treated with saline solution and suggested the drug had a sedative effect. Plasma hydromorphone concentrations were > 1 ng/mL for 3 to 6 hours after drug administration in all birds. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that IM administration of hydromorphone at the evaluated doses did not increase the thermal withdrawal threshold of cockatiels despite plasma drug concentrations considered therapeutic for other species. Further research is necessary to evaluate the analgesic effects of hydromorphone in cockatiels.

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.

PHARMACOKINETIC EVALUATION OF A LONG-ACTING FENTANYL SOLUTION AFTER TRANSDERMAL ADMINISTRATION IN HELMETED GUINEAFOWL (NUMIDA MELEAGRIS)

The objective of this study was to investigate the pharmacokinetics of a long-acting fentanyl solution in helmeted guineafowl ( Numida meleagris ) after transdermal administration. Twenty-one guineafowl received a single administration of 5 mg/kg of fentanyl transdermal solution. No adverse effects on behavior were appreciated. Plasma fentanyl concentrations were determined by liquid chromatography-mass spectrometry analysis of protein-precipitated samples. Mean maximum plasma concentration was 228.8 ng/ml at 4 hr. The mean plasma terminal half-life was 33.2 hr. At 168 hr the mean plasma concentration was 1.3 ng/ml. A single topical dose of 5 mg/kg appears to be safe for use in this species and maintained plasma concentrations above those reported to be analgesic in dogs for at least 7 days.

Wildlife Emergency and Critical Care

Wildlife patients often present as emergencies. For veterinarians who do not typically treat wildlife, it is important to be able to stabilize and determine the underlying cause of the animal's signs. This article discusses initial assessment, stabilization, and treatment of common emergency presentations in wild birds, reptiles, and mammals.

Pharmacokinetics of tramadol following intravenous and oral administration in male rhesus macaques (Macaca mulatta)

Recently, tramadol and its active metabolite, O-desmethyltramadol (M1), have been studied as analgesic agents in various traditional veterinary species (e.g., dogs, cats, etc.). This study explores the pharmacokinetics of tramadol and M1 after intravenous (IV) and oral (PO) administration in rhesus macaques (Macaca mulatta), a nontraditional veterinary species. Rhesus macaques are Old World monkeys that are commonly used in biomedical research. Effects of tramadol administration to monkeys are unknown, and research veterinarians may avoid inclusion of this drug into pain management programs due to this limited knowledge. Four healthy, socially housed, adult male rhesus macaques (Macaca mulatta) were used in this study. Blood samples were collected prior to, and up to 10 h post-tramadol administration. Serum tramadol and M1 were analyzed using liquid chromatography-mass spectrometry. Noncompartmental pharmacokinetic analysis was performed. Tramadol clearance was 24.5 (23.4-32.7) mL/min/kg. Terminal half-life of tramadol was 111 (106-127) min IV and 133 (84.9-198) min PO. Bioavailability of tramadol was poor [3.47% (2.14-5.96%)]. Maximum serum concentration of M1 was 2.28 (1.88-2.73) ng/mL IV and 11.2 (9.37-14.9) ng/mL PO. Sedation and pruritus were observed after IV administration.

Evaluation of thermal antinociceptive effects after oral administration of tramadol hydrochloride to American kestrels (Falco sparverius)

OBJECTIVE

To evaluate the thermal antinociceptive and sedative effects and duration of action of tramadol hydrochloride after oral administration to American kestrels (Falco sparverius).

ANIMALS

12 healthy 3-year-old American kestrels.

PROCEDURES

Tramadol (5, 15, and 30 mg/kg) and a control suspension were administered orally in a masked randomized crossover experimental design. Foot withdrawal response to a thermal stimulus was determined 1 hour before (baseline) and 0.5, 1.5, 3, 6, and 9 hours after treatment. Agitation-sedation scores were determined 3 to 5 minutes before each thermal stimulus test.

RESULTS

The lowest dose of tramadol evaluated (5 mg/kg) significantly increased the thermal foot withdrawal thresholds for up to 1.5 hours after administration, compared with control treatment values, and for up to 9 hours after administration, compared with baseline values. Tramadol at doses of 15 and 30 mg/kg significantly increased thermal thresholds at 0.5 hours after administration, compared with control treatment values, and up to 3 hours after administration, compared with baseline values. No significant differences in agitation-sedation scores were detected between tramadol and control treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated oral administration of 5 mg of tramadol/kg significantly increased thermal nociception thresholds for kestrels for 1.5 hours, compared with a control treatment, and 9 hours, compared with baseline values; higher doses resulted in less pronounced antinociceptive effects. Additional studies with other types of stimulation, formulations, dosages, routes of administration, and testing times would be needed to fully evaluate the analgesic and adverse effects of tramadol in kestrels and other avian species.

Evaluation of thermal antinociceptive effects and pharmacokinetics after intramuscular administration of butorphanol tartrate to American kestrels (Falco sparverius)

OBJECTIVE

To evaluate antinociceptive effects and pharmacokinetics of butorphanol tartrate after IM administration to American kestrels (Falco sparverius).

ANIMALS

Fifteen 2- to 3-year-old American kestrels (6 males and 9 females).

PROCEDURES

Butorphanol (1, 3, and 6 mg/kg) and saline (0.9% NaCl) solution were administered IM to birds in a crossover experimental design. Agitation-sedation scores and foot withdrawal response to a thermal stimulus were determined 30 to 60 minutes before (baseline) and 0.5, 1.5, 3, and 6 hours after treatment. For the pharmacokinetic analysis, butorphanol (6 mg/kg, IM) was administered in the pectoral muscles of each of 12 birds.

RESULTS

In male kestrels, butorphanol did not significantly increase thermal thresholds for foot withdrawal, compared with results for saline solution administration. However, at 1.5 hours after administration of 6 mg of butorphanol/kg, the thermal threshold was significantly decreased, compared with the baseline value. Foot withdrawal threshold for female kestrels after butorphanol administration did not differ significantly from that after saline solution administration. However, compared with the baseline value, withdrawal threshold was significantly increased for 1 mg/kg at 0.5 and 6 hours, 3 mg/kg at 6 hours, and 6 mg/kg at 3 hours. There were no significant differences in mean sedation-agitation scores, except for males at 1.5 hours after administration of 6 mg/kg.

CONCLUSION AND CLINICAL RELEVANCE

Butorphanol did not cause thermal antinociception suggestive of analgesia in American kestrels. Sex-dependent responses were identified. Further studies are needed to evaluate the analgesic effects of butorphanol in raptors.

Pharmacokinetics of tramadol and its primary metabolite O-desmethyltramadol in African penguins (Spheniscus demersus)

Analgesia is an important part of veterinary medicine, but until recently there have been limited studies on analgesic drugs in avian species. Tramadol represents an orally administered opioid drug that has shown analgesic potential in numerous species, including mammals, birds, and reptiles. The objective of this study was to determine the pharmacokinetic parameters of tramadol and its primary metabolite, O-desmethyltramadol (M1), after oral administration of tramadol hydrochloride (HCl) in African penguins (Spheniscus demersus). A dose of 10 mg/kg of tramadol HCl was administered orally to 15 birds, and blood was collected at various time points from 0 to 36 hr. Tramadol and M1 concentrations were determined and were consistent with therapeutic concentrations in humans through 12 hr in 9/15 birds for tramadol and 36 hr in 14/15 birds for M1. Based on these findings and a comparison with other avian studies, an oral dose of 10 mg/kg of tramadol once daily appears to be a promising analgesic option for African penguins.

Pharmacokinetics of repeated oral administration of tramadol hydrochloride in Hispaniolan Amazon parrots (Amazona ventralis)

OBJECTIVE

To determine the pharmacokinetics of tramadol hydrochloride (30 mg/kg) following twice-daily oral administration in Hispaniolan Amazon parrots (Amazona ventralis).

ANIMALS

9 healthy adult Hispaniolan Amazon parrots.

PROCEDURES

Tramadol hydrochloride was administered to each parrot at a dosage of 30 mg/kg, PO, every 12 hours for 5 days. Blood samples were collected just prior to dose 2 on the first day of administration (day 1) and 5 minutes before and 10, 20, 30, 60, 90, 180, 360, and 720 minutes after the morning dose was given on day 5. Plasma was harvested from blood samples and analyzed by high-performance liquid chromatography. Degree of sedation was evaluated in each parrot throughout the study.

RESULTS

No changes in the parrots' behavior were observed. Twelve hours after the first dose was administered, mean ± SD concentrations of tramadol and its only active metabolite M1 (O-desmethyltramadol) were 53 ± 57 ng/mL and 6 ± 6 ng/mL, respectively. At steady state following 4.5 days of twice-daily administration, the mean half-lives for plasma tramadol and M1 concentrations were 2.92 ± 0.78 hours and 2.14 ± 0.07 hours, respectively. On day 5 of tramadol administration, plasma concentrations remained in the therapeutic range for approximately 6 hours. Other tramadol metabolites (M2, M4, and M5) were also present.

CONCLUSIONS AND CLINICAL RELEVANCE

On the basis of these results and modeling of the data, tramadol at a dosage of 30 mg/kg, PO, will likely need to be administered every 6 to 8 hours to maintain therapeutic plasma concentrations in Hispaniolan Amazon parrots.

Pharmacokinetics after oral and intravenous administration of a single dose of tramadol hydrochloride to Hispaniolan Amazon parrots (Amazona ventralis)

OBJECTIVE

To determine pharmacokinetics after IV and oral administration of a single dose of tramadol hydrochloride to Hispaniolan Amazon parrots (Amazona ventralis).

ANIMALS

9 healthy adult Hispaniolan Amazon parrots (3 males, 5 females, and 1 of unknown sex).

PROCEDURES

Tramadol (5 mg/kg, IV) was administered to the parrots. Blood samples were collected from -5 to 720 minutes after administration. After a 3-week washout period, tramadol (10 and 30 mg/kg) was orally administered to parrots. Blood samples were collected from -5 to 1,440 minutes after administration. Three formulations of oral suspension (crushed tablets in a commercially available suspension agent, crushed tablets in sterile water, and chemical-grade powder in sterile water) were evaluated. Plasma concentrations of tramadol and its major metabolites were measured via high-performance liquid chromatography.

RESULTS

Mean plasma tramadol concentrations were > 100 ng/mL for approximately 2 to 4 hours after IV administration of tramadol. Plasma concentrations after oral administration of tramadol at a dose of 10 mg/kg were < 40 ng/mL for the entire time period, but oral administration at a dose of 30 mg/kg resulted in mean plasma concentrations > 100 ng/mL for approximately 6 hours after administration. Oral administration of the suspension consisting of the chemical-grade powder resulted in higher plasma tramadol concentrations than concentrations obtained after oral administration of the other 2 formulations; however, concentrations differed significantly only at 120 and 240 minutes after administration.

CONCLUSIONS AND CLINICAL RELEVANCE

Oral administration of tramadol at a dose of 30 mg/kg resulted in plasma concentrations (> 100 ng/mL) that have been associated with analgesia in Hispaniolan Amazon parrots.