Pharmacokinetics of a Sustained-release Formulation of Meloxicam After Subcutaneous Administration to Hispaniolan Amazon Parrots (Amazona ventralis)

Determining the Pharmacokinetic Properties of Two Different Doses of Meloxicam in Barred Owls (Strix varia)

Anthropogenic activities have negatively affected many birds, including owls. The Wildlife Hospital of Louisiana (WHL) has seen a 3.2-fold increase in barred owl (Strix varia) cases over the past eight years (2023, 134; 2015, 42). Because most of these animals present with traumatic injuries, analgesics should be considered in their treatment plan. To date, no study has measured the pharmacokinetics of an analgesic in barred owls. The goals of this study were to determine the harmonic means, times to maximum concentration, and elimination half-lives for single 1 mg/kg and 2 mg/kg intramuscular doses of meloxicam. Twelve barred owls (1 mg/kg, n = 6; 2 mg/kg, n = 6) admitted to the WHL and determined to be clinically normal based on examination and blood work were recruited for this study. Meloxicam was administered intramuscularly, and blood samples were collected intermittently over 12 h to measure plasma concentrations using high-performance liquid chromatography. Both doses had rapid elimination half-lives (1 mg/kg, 0.99 ± 0.1 h; 2 mg/kg, 1.07 ± 0.43 h) and were below the limits of quantification (0.1 µg/mL) by 6-12 h. Based on these results, 1 and 2 mg/kg doses of meloxicam were found to produce plasma concentrations below therapeutic concentrations for less than four hours, making current twice-daily recommended dosing intervals unlikely to provide desired analgesia.

Long-Acting Drug Delivery Technologies for Meloxicam as a Pain Medicine

Meloxicam, a selective COX-2 inhibitor, has demonstrated clinical effectiveness in managing inflammation and acute pain. Although available in oral and parenteral formulations such as capsule, tablet, suspension, and solution, frequent administration is necessary to maintain therapeutic efficacy, which can increase adverse effects and patient non-compliance. To address these issues, several sustained drug delivery strategies such as oral, transdermal, transmucosal, injectable, and implantable drug delivery systems have been developed for meloxicam. These sustained drug delivery strategies have the potential to improve the therapeutic efficacy and safety profile of meloxicam, thereby reducing the frequency of dosing and associated gastrointestinal side effects. The choice of drug delivery system will depend on the desired release profile, the target site of inflammation, and the mode of administration. Overall, meloxicam sustained delivery systems offer better patient compliance, and reduce the side effects, thereby improving the clinical applications of this drug. Herein, we discuss in detail different strategies for sustained delivery of meloxicam.

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 (Vdss ) of 206.50 ± 25.23 ml/kg, a terminal half-life (t1/2λ ) 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 (Cmax 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.

Pharmacokinetics of maropitant citrate in Rhode Island Red chickens (Gallus gallus domesticus) following subcutaneous administration

Maropitant citrate is a synthetic neurokinin‐1 receptor antagonist and substance P inhibitor used for control of emesis in dogs in cats. Maropitant citrate is used empirically in birds, despite a lack of pharmacokinetic data in avian species. The objective of this study was to determine the pharmacokinetic profile of a single dose of maropitant citrate 1 and 2 mg/kg subcutaneously (SC) in eight Rhode Island Red hens (Gallus gallus domesticus). A crossover study design was used with 1‐week washout between trials. Blood samples were collected over 36 h after drug administration. Plasma concentrations were measured using liquid chromatography–tandem mass spectrometry and pharmacokinetic parameters were determined via non‐compartmental analysis. The mean maximum plasma concentration, time to maximum concentration, and elimination half‐life following 1 and 2 mg/kg SC were 915.6 ± 312.8 ng/ml and 1195.2 ± 320.2 ng/ml, 0.49 ± 0.21 h and 1.6 ± 2.6 h, and 8.47 ± 2.24 h and 8.58 ± 2.6 h, respectively. Pharmacokinetic data suggests doses of 1 or 2 mg/kg SC may be administered every 12–24 h to maintain above target plasma concentration similar to dogs (90 ng/ml). These data provide a basis for further investigation of maropitant citrate pharmacokinetics and pharmacodynamics in birds.

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.

Preliminary Investigation into a Novel Sustained-Release Formulation of Meloxicam in Sheep (Ovis aries)-Pharmacokinetic Profile

Simple Summary

Meloxicam is an effective non-steroidal anti-inflammatory drug (NSAID) suitable for ameliorating pain in sheep. Pain caused by husbandry procedures and other inflammatory conditions in sheep can persist for an extended time beyond the duration of action of currently available formulations of NSAIDs. This study investigates a novel sustained-release formulation of meloxicam to determine its potential for extended pain alleviation. Compared to a conventional formulation of meloxicam, the sustained-release formulation provided extended half-life making it a suitable candidate for providing extended pain relief.

Abstract

This study is a preliminary investigation describing the pharmacokinetic profile of a novel subcutaneous sustained-release meloxicam formulation (SRMF) in sheep. Six merino ewe hoggets (41.5 ± 4.6 kg) were treated with a novel subcutaneous SRMF at 2 mg/kg bodyweight (BW). Blood samples were collected at t = 0, 2, 4, 6, 8, 10, 12, 24, 48, 96, 144, 168, 192, and 336 h following treatment, and interstitial (ISF) fluid samples were collected at periods of 8 to 12 h, 12 to 24 h, 24 to 48 h, 48 to 52 h, and 92 to 96 h following treatment. High-pressure liquid chromatography (HPLC) analysis with ultraviolet detection was utilised to determine the concentration of meloxicam in plasma and ISF. The SRMF exhibited the following mean (±SD) pharmacokinetic indices: C_max of 1.58 μg/mL (±0.82 μg/mL) at a T_max of 10.0 h (±1.79 h), and half life (t_1/2) of 31.4 h (±13.17 h) in sheep plasma. Interstitial fluid samples were collected from three of the six sheep, with a decrease in meloxicam concentration exhibited over 52 h. This study demonstrates a variable extended t_1/2, a delayed T_max, and a lower C_max of the SRMF, as compared to that of a conventional meloxicam formulation (CMF) in sheep, as previously referenced (t_1/2: 14.28 h; T_max: 5 h; C_max: 15.94 μg/mL). Further research to determine the clinical efficacy and safety of the SRMF in sheep is warranted.

Injection-site Reactions to Sustained-release Meloxicam in Sprague-Dawley Rats

An extended-release formulation of the NSAID meloxicam (MSR) is used to provide 72 h of continuous analgesia in many species, including rodents. Although standard formulations of meloxicam are frequently used in rats with no observable injection-site reactions, the potential adverse effects from MSR have not been characterized sufficiently nor has a prospective study of these effects been performed in rats. To address this deficiency, we evaluated injection-site reactions after a single subcutaneous administration of MSR (n = 16) or sterile saline (SC, n = 6) in the flank of age- and sex-matched Sprague-Dawley rats. Mass and erythema scores were measured daily for 2 wk, and injection sites were collected for histopathology after euthanasia. Rats were randomly selected for euthanasia at 7 d (n = 12) or 14 d (n = 10) after injection to capture the subacute and chronic phases of mass and erythematic lesion formation. No rats in the SC group developed lesions, whereas all 16 MSR-treated rats developed masses. The median time to first mass in the MSR treatment group was 3 d (95% CI, 2-3 d), and nearly 8 d for erythema (95% CI, 6.7-9.1 d). The trajectory of mass lesion severity showed rapid progression from score 1 at onset (day 2 or 3) to score 2 for almost all animals by day 5 or 6. Histopathology was characterized by localized inflammation with central necrosis and peripheral fibrosis, with some sections showing developing draining tracts. Given the high prevalence and severity of localized skin reactions, MSR analgesia should be considered carefully for Sprague-Dawley rats.

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 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.

Preliminary Evaluation of Sustained-release Compared with Conventional Formulations of Meloxicam in Sheep (Ovis aries)

Sustained-release (SR) drugs refine current analgesic regimens by alleviating the need for multiple sessions of handling and restraint and by reducing the local tissue irritation that can occur due to repeated injections. Although a variety of SR drugs are already used in lab animal medicine, no studies exist that evaluate the suitability of an SR NSAID in sheep. This study used HPLC-MS to measure the plasma concentrations of 2 formulations of meloxicam-conventional and SRM- after subcutaneous administration in 6 adult ewes. Blood was collected at 0, 4, 12, 24, 36, 48, 60, 72, 84, 96, 120, 144, and 168 h after injection. In addition, physical exams, urinalysis, and biochemical analysis were performed at 0, 24, 48, and 120 h after dosage. Peak plasma concentrations were 1057 ± 433 ng/mL at 4 ± 0 h for conventional meloxicam and 3238 ± 1480 ng/mL at 6.7 ± 4.1 h for SR meloxicam (SRM). Elimination half-lives were 12.1 4.2 for CM and 15.2 ± 2.4 h for SRM. One sheep had an episode of acute renal azotemia starting 24 h after SRM administration; the episode resolved over time, and the definitive relationship to SRM administration was not determined. Plasma levels of SRM were higher than CM throughout the initial 24 h, remained variably elevated until 60 h after injection, but failed to sustain presumed therapeutic levels of 400 ng/mL for the full 72 h across all animals in this study. Further investigation is warranted to determine the safety and clinical efficacy of SRM in sheep. Currently, when SRM is used in sheep, we recommend the combination of a preemptive and multimodal analgesia regimen with clinical assessments throughout the postoperative period.