Pain-Suppressed Behaviors in the Red-tailed Hawk (Buteo jamaicensis)

Pain Recognition and Assessment in Birds

The recognition and assessment of pain in avian species are crucial tools in providing adequate supportive care in clinical, laboratory, zoologic, rehabilitation, and companion animal settings. With birds being a highly diverse class of species, there is still much to be determined regarding how to create specific criteria to recognize and assess pain in these animals. This article provides a clinical review on the physiology of pain in birds, observed behavioral and physiologic alterations with pain, how different sources and degrees of pain can alter behaviors observed, and how this information can be applied in a clinical setting.

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.

A comparative study on anti-inflammatory drug combinations in domestic pigeons with experimentally induced acute arthritis

The study compares the effect of one-time administration of nonsteroidal and/or steroidal anti-inflammatory combinations by topical or intramuscular (IM) routes to pigeons with monosodium urate (MSU)-induced arthritis. Forty-five adult domestic pigeons were assigned into nine equal groups: NC, negative control; PC, positive control with arthritis; sham, sham control; T1, meloxicam + hydrocortisone; T2, dexamethasone + piroxicam; T3, meloxicam + dexamethasone; T4, hydrocortisone + piroxicam; T5, dexamethasone + hydrocortisone; T6, meloxicam + piroxicam. Arthritis was also induced in T1 to T6 birds. Meloxicam and dexamethasone were administered by IM injection and the other drugs topically right after the induction of arthritis. Different drug combinations significantly decreased one-leg standing time. Induction of arthritis significantly increased TNF-α and IL-6 levels in synovial fluid and serum corticosterone and epinephrine in the PC group. Administration of drugs to birds of Groups T1 and T5 did not significantly change corticosterone concentration, while all different drug combinations decreased epinephrine level. Drug combinations that demonstrated better analgesic effect more strongly reduced serum epinephrine concentration. Meloxicam + hydrocortisone was the most effective combination in reducing inflammatory cytokines. In conclusion, one-time combination therapy with anti-inflammatory agents was effective in the acute management of inflammatory pain due to MSU-induced arthritis in pigeons, even by the topical route.

Pharmacokinetics of a concentrated buprenorphine formulation in red-tailed hawks (Buteo jamaicensis)

OBJECTIVE To determine the pharmacokinetics and sedative effects of 2 doses of a concentrated buprenorphine formulation after SC administration to red-tailed hawks (Buteo jamaicensis). ANIMALS 6 adult red-tailed hawks. PROCEDURES Concentrated buprenorphine (0.3 mg/kg, SC) was administered to all birds. Blood samples were collected at 10 time points over 24 hours after drug administration to determine plasma buprenorphine concentrations. After a 4-week washout period, the same birds received the same formulation at a higher dose (1.8 mg/kg, SC), and blood samples were collected at 13 time points over 96 hours. Hawks were monitored for adverse effects and assigned agitation-sedation scores at each sample collection time. Plasma buprenorphine concentrations were quantified by liquid chromatography-tandem mass spectrometry. RESULTS Mean time to maximum plasma buprenorphine concentration was 7.2 minutes and 26.1 minutes after administration of the 0.3-mg/kg and 1.8-mg/kg doses, respectively. Plasma buprenorphine concentrations were > 1 ng/mL for mean durations of 24 and 48 hours after low- and high-dose administration, respectively. Mean elimination half-life was 6.23 hours for the low dose and 7.84 hours for the high dose. Mean agitation-sedation scores were higher (indicating some degree of sedation) than the baseline values for 24 hours at both doses. No clinically important adverse effects were observed. CONCLUSIONS AND CLINICAL RELEVANCE Concentrated buprenorphine was rapidly absorbed, and plasma drug concentrations considered to have analgesic effects in other raptor species were maintained for extended periods. Most birds had mild to moderate sedation. Additional studies are needed to evaluate the pharmacodynamics of these doses of concentrated buprenorphine in red-tailed hawks.

Pharmacokinetics of a Sustained Release Formulation of Buprenorphine After Intramuscular and Subcutaneous Administration to American Kestrels ( Falco sparverius )

Previous studies have validated the clinical use of opioids with μ-receptor affinities for pain management in raptors. Buprenorphine appears to have a longer duration of action and minimal adverse effects when compared to other opioids in American kestrels ( Falco sparverius ). To determine the pharmacokinetics of a sustained release formulation of buprenorphine in kestrels, we administered a commercially available product (Buprenorphine SR-LAB; Wildlife Pharmaceuticals, Windsor, CO, USA) intramuscularly and subcutaneously to adult kestrels in a partial-crossover experimental design study. A total of 12 birds (6 males and 6 females) were assigned randomly to 3 groups of 4 birds each. A single dose of Buprenorphine SR-LAB (1.8 mg/kg) was administered intramuscularly (IM), and blood samples were collected at 0.25, 3, and 24 hours (n = 4); 1, 6, and 48 hours (n = 4); and 2, 12, and 72 hours (n = 4) after drug administration. Plasma buprenorphine concentrations were measured by tandem liquid chromatography-mass spectrometry. Pharmacokinetic parameters were determined by use of least squares linear regression and noncompartmental analysis of naïve pooled data. After 1 year, the same dose of buprenorphine was administered subcutaneously (SC) to 12 birds divided into 3 groups as previously, and blood samples were collected at the same times after drug administration. Maximum plasma buprenorphine concentration was measured at 15 minutes after IM and SC administration. Mean plasma buprenorphine concentrations were >1 ng/mL for 48 hours after IM and SC administration. The elimination half-life was 13.5 and 11.1 hours for IM and SC administration, respectively. Depending on the severity and type of pain, adjunctive therapy, and the individual response, Buprenorphine SR-LAB administered at 1.8 mg/kg IM or SC to American kestrels would require administration every 12 to 72 hours to manage pain. Further pharmacodynamic and clinical evaluations are warranted in kestrels and other raptors to establish accurate dosing recommendations.

Pharmacokinetics of buprenorphine hydrochloride following intramuscular and intravenous administration to American kestrels (Falco sparverius)

OBJECTIVE

To determine the pharmacokinetics of buprenorphine hydrochloride after IM and IV administration to American kestrels (Falco sparverius).

ANIMALS

13 healthy 3-year-old captive-bred American kestrels.

PROCEDURES

Buprenorphine hydrochloride (0.6 mg/kg) was administered IM to all birds. Blood samples were collected at 9 times, ranging from 5 minutes to 9 hours after drug administration. Plasma buprenorphine concentrations were measured by use of tandem liquid chromatography-mass spectrometry. Pharmacokinetic parameters were determined by use of least squares linear regression and noncompartmental analysis of naïve pooled data. After a washout period of 2 weeks, the same dose of buprenorphine was administered IV to all birds and blood samples were collected at the same times after drug administration.

RESULTS

Maximum plasma buprenorphine concentration was achieved within 5 minutes after IM administration. For IM administration, bioavailability was 94.8% and elimination half-life was 92.1 minutes. For IV administration, steady-state volume of distribution was 4,023.8 mL/kg, plasma clearance was 49.2 mL/min/kg, and elimination half-life was 105.5 minutes.

CONCLUSIONS AND CLINICAL RELEVANCE

Buprenorphine was rapidly absorbed, and bioavailability was good after IM administration to American kestrels. Plasma buprenorphine concentrations were > 1 ng/mL for 9 hours after both IM and IV administration. These results, in combination with those of a pharmacodynamic study, suggested that the analgesic effects of buprenorphine could last at least 6 to 9 hours in this species. Further investigations of the duration of analgesic effects, multiple-dose protocols, and potential adverse effects of buprenorphine are warranted in American kestrels and other raptors.