Pharmacokinetics of meloxicam after intramuscular and oral administration of a single dose to American flamingos (Phoenicopertus ruber)

Pharmacokinetics of meloxicam in pigeons after single intravenous, oral, and intramuscular administration

This study aimed to determine the pharmacokinetics of meloxicam in pigeons. Twenty-four 7-wk-old meat pigeons (Columba livia) were randomly divided into 3 groups (PO, IM, and IV) and given a single dose of 1 mg/kg body weight of meloxicam. Plasma samples were taken at predetermined times, which were then analyzed using a validated high-performance liquid chromatography (HPLC) method and subjected to noncompartmental analysis using Phoenix software. Results indicated that meloxicam was absorbed effectively and quickly after PO and IM dosing. Peak concentrations (0.83 ± 0.21 and 1.59 ± 0.49 μg/mL) were achieved at 2 and 0.26 h, respectively, with mean absorption times of 2.56 ± 1.50 and 1.47 ± 0.89 h. Bioavailability was high at 86.31 ± 43.45% and 81.57 ± 52.58%, respectively, and the area under the concentration-time curve (AUC0-∞) was 5.33 ± 2.68 and 5.03 ± 3.26 h·µg/mL. After IV administration, the elimination was faster with a total body clearance (CL) of 188.75 ± 83.23 mL/h/kg, an elimination half-life (t1/2λz) of 1.76 ± 0.56 h, and a volume of distribution at steady-state (VSS) of 427.50 ± 188.43 mL/kg. Considering the lack of a precise analgesic threshold of meloxicam in pigeons and the notable differences in its analgesic threshold among various animal species, formulating a dosing regimen in pigeons presented a significant challenge. Based on the previous analgesic threshold (3.5 μg/mL) in parrots, a higher dose (e.g., 2 mg/kg) or shorter dosing interval (e.g., every 6 h) is recommended for treating pain in pigeons. Nonetheless, further pharmacodynamic research is required to verify these recommendations.

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.

Pharmacokinetics of meloxicam in laying hens after single intravenous, oral, and intramuscular administration

The objective of this study was to determine the pharmacokinetics of meloxicam after a single intravenous (IV), intramuscular (IM), and oral (PO) dose at 1 mg/kg body weight in Jing Hong laying hens. Blood samples were collected at predetermined time points. Plasma meloxicam concentrations were determined using a validated high-performance liquid chromatography (HPLC) assay method and then subjected to a non-compartmental analysis. After IV administration, meloxicam had a mean (±SD) volume of distribution at steady-state (Vd_ss ) of 206.50 ± 25.23 ml/kg, a terminal half-life (t_1/2λ ) of 5.45 ± 0.53 h, and a total body clearance (Cl) of 26.48 ± 4.13 ml/h/kg. After PO and IM administration, meloxicam was absorbed relatively rapidly: the peak concentrations (C_max s) of 3.04 ± 0.56 and 8.94 ± 2.31 μg/ml were observed at 3.08 and 0.80 h, respectively. After PO and IM administration, the absolute bioavailability (F) was determined as 70.13% and 125.50%, respectively. Assuming that hens shared the same analgesic threshold of meloxicam (0.5 μg/ml) with humans, the plasma concentrations after three different routes (PO, IM, and IV) of administration were above this value for 16.7, 19.2, and 14.9 h, respectively.

A Critical Review of the Pharmacokinetics, Pharmacodynamics, and Safety Data of Antibiotics in Avian Species

In avian medicine, the use of antibiotic dosing regimens based on species-specific pharmacological studies is ideal. However, due to a lack of such studies, dose extrapolation, which may cause inefficacy and toxicity, is common practice. Multiple searches were performed using the PubMed and Web of Science databases to extract relevant pharmacological studies performed in exotic avian species. The pharmacokinetics (PK), pharmacodynamics (PD), and safety data of the selected antibiotics (enrofloxacin, marbofloxacin, gentamicin, amikacin, ceftiofur, doxycycline, and amoxicillin/clavulanate) from these studies were reviewed. This review aimed to identify trends amenable for safe inter-species dose extrapolation and provide updated findings on dosing regimens that are safe and efficacious for various exotic avian species. We observed that the half-life of antibiotics appears to be shorter in the common ostrich and that amikacin may be amenable to inter-species dose extrapolation as it is safe and shows little inter-species PK and PD variation. Species-specific enrofloxacin dosing regimens that were not listed in the Exotic Animal Formulary (5th ed.) were found for Caribbean flamingos, African penguins, southern crested caracaras, common ostriches, and greater rheas. Specific dosing regimens recommended for psittacine birds (doxycycline 130 mg/kg medicated water) and ratites (PO doxycycline 2–3.5 mg/kg q12 h, PO enrofloxacin 1.5–2.5 mg/kg q12 h and IM enrofloxacin 5 mg/kg q12 h) in the formulary may not be effective in budgerigars and common ostriches, respectively. Apart from the lack of species-specific pharmacological studies, a lack of multiple dose studies was also noted.

Pharmacokinetic Parameters and Estimating Extra-Label Tissue Withdrawal Intervals Using Three Approaches and Various Matrices for Domestic Laying Chickens Following Meloxicam Administration

Meloxicam is commonly prescribed for treating chickens in backyard or small commercial operations despite a paucity of scientific data establishing tissue withdrawal interval recommendations following extra-label drug use (ELDU). Historically, ELDU withdrawal intervals (WDIs) following meloxicam administration to chickens have been based on the time when meloxicam concentrations fall below detectable concentrations in plasma and egg samples. To date, no studies have addressed tissue residues. ELDU WDIs are commonly calculated using terminal elimination half-lives derived from pharmacokinetic studies. This study estimated pharmacokinetic parameters for laying hens following meloxicam administration and compared ELDU WDIs calculated using tissue terminal elimination half-lives vs. those calculated using FDA tolerance and EMA's maximum regulatory limit statistical methods, respectively. In addition, ELDU WDIs were calculated using plasma meloxicam concentrations from live birds to determine if plasma data could be used as a proxy for estimating tissue WDIs. Healthy domestic hens were administered meloxicam at 1 mg/kg intravenous (IV) once, 1 mg/kg orally (PO) once daily for eight doses or 1 mg/kg PO twice daily for 20 doses. Analytical method validation was performed and meloxicam concentrations were quantified using high-performance liquid chromatography. In general, the terminal elimination technique resulted in the longest ELDU WDIs, followed by the FDA tolerance and then EMA's maximum residue limit methods. The longest ELDU WDIs were 72, 96, and 384 (or 120 excluding fat) h for the IV, PO once daily for eight doses, and PO twice daily for 20 doses, respectively. Plasma data are a possible dataset for estimating a baseline for tissue ELDU WDI estimations when tissue data are not available for chickens treated with meloxicam. Finally, pharmacokinetic parameters were similar in laying hens to those published for other avian 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.

Pharmacokinetics and Safety of Intramuscular Meloxicam in Zebra Finches (Taeniopygia guttata)

Meloxicam is the most frequently used NSAID in birds; however, its elimination t_1/2 is highly variable among species. Because zebra finches that require analgesia could benefit from receiving meloxicam, we performed a pharmacokinetic study involving a single intramuscular dose of 1 or 2 mg/kg. Data analysis showed that C_max, t_1/2, and elimination rate constants were not significantly different between the 2 doses. In contrast, C_max for 1- and 2-mg/kg doses of meloxicam approached a significant difference, and those for AUC_0-∞ were significantly different. Importantly, a plasma concentration of 3500 ng/mL, considered a target level for meloxicam in other avian species, was maintained for approximately 9.5 h in finches that received 2 mg/kg, which was 4 h longer than in birds given 1 mg/kg. Both doses reached low plasma concentrations by 12 h after administration. Subsequently, 8 total doses of 1 or 2 mg/kg were administered to birds at 12-h intervals; these regimens caused no significant changes in select biochemical analytes or the Hct of meloxicam-treated birds. In addition, histopathologic changes for injection sites, kidney, liver, proventriculus, and ventriculus were minimal and similar between control and experimental groups after the multiple doses. These results suggest a 12-h or more frequent dosing interval is likely needed in zebra finches and that meloxicam at 1 or 2 mg/kg IM twice daily for 4 d is safe. The higher dose might provide longer analgesia compared with the lower dose, but a pharmacodynamics evaluation of meloxicam in zebra finches is needed to confirm analgesic efficacy.

PHARMACOKINETICS OF A SUSTAINED-RELEASE FORMULATION OF MELOXICAM AFTER SUBCUTANEOUS ADMINISTRATION TO AMERICAN FLAMINGOS ( PHOENICOPTERUS RUBER)

Meloxicam is commonly used in avian medicine to relieve pain and inflammation, but the recommended dosing frequency can be multiple times per day, which can contribute to stress during convalescence. In this study, the pharmacokinetics of a sustained-release formulation of meloxicam were determined after subcutaneous administration of a single 3-mg/kg dose to eight healthy adult American flamingos ( Phoenicopterus ruber). Blood samples were collected before (time 0) and at 0.5, 1, 4, 8, 12, 24, 48, 96, and 120 hr after drug administration. Analysis of meloxicam in plasma samples was conducted with the use of reversed-phase high-performance liquid chromatography, and pharmacokinetic parameters were calculated by noncompartmental analysis. Plasma concentrations reached a mean maximum (±standard deviation) of 7.65 (±2.39) μg/ml at 0.56 (±0.18) hr with a terminal half-life of 1.76 (±1.41) hr. Based on these findings, this sustained-release formulation of meloxicam does not extend the interval between treatments as compared to the regular formulation, so it is not recommended in American flamingos at this time.

PHARMACOKINETICS OF ORAL GABAPENTIN IN CARIBBEAN FLAMINGOS ( PHOENICOPTERUS RUBER RUBER)

Gabapentin is a first-line treatment for neuropathic pain and adjunct anticonvulsant medication in humans and other species. Gabapentin may have advantages over other analgesics because of its broad therapeutic range with limited adverse effects and wide availability as an oral formulation. This study determined the pharmacokinetics of gabapentin in Caribbean flamingos ( Phoenicopterus ruber ruber) after a single-dose oral administration of either 15 mg/kg ( n = 6) or 25 mg/kg ( n = 6). Plasma gabapentin concentrations were determined using liquid chromatography with mass spectrometry, and pharmacokinetic analysis was performed using noncompartmental methods. Respectively for the 15 mg/kg and 25 mg/kg dose, mean peak plasma concentration ( C_max) was (mean ± pseudo SD) 13.23 ± 1.47 and 24.48 ± 5.81 μg/ml; mean time to peak plasma concentration ( T_max) was 0.50 ± 0.24 and 0.56 ± 0.28 hr; mean area under the curve (AUC) was 76.0 ± 26.3 and 114.7 ± 27.5 hr·μg/ml; and mean terminal half-life ( T_1/2) was 3.39 ± 0.90 and 4.46 ± 1.12 hr. Based on the results of this study, gabapentin dosed at 25 mg/kg orally in most Caribbean flamingos is likely to maintain plasma concentrations above the therapeutic range established for humans for approximately 12 hr.