Pharmacokinetics & Bioavailability of Meloxicam in Ring-necked Parakeets
Presenting Author: Heather Wilson, DVM, Dipl ABVP (Avian),et al
Department of Small Animal Medicine, University of Georgia, GA
Interpretive Review and comments by Dr. Nemetz:
Reduction of pain and inflammation is an important part of medical and surgical management in all patients including the avian patient. However, information on the pharmacokinetics or pharmacodynamics of anti-inflammatory drugs in birds is relatively scarce. Birds are known to be very sensitive to the deleterious side effects of steroids, so non-steroidal anti-inflammatory drugs (NSAIDs) often are more appropriate as they exert their effects through different biochemical pathways.
Meloxicam (Metacam) has been used for years in Europe, used by avian veterinarians in the United States by compounding the human tablets, but now is an approved veterinary drug. It is only licensed for use only in dogs. This still means veterinarians must use this drug as an "off-label" use, however now it is produced as an oral suspension.
Meloxicam and other NSAIDs (Celecoxib, Carprofen) have been used empirically in psittacine species based on mammalian data but the author's goal was to add science to Meloxicam's effects in at least one psittacine species: Ring-necked parakeets.
Meloxicam was administered intravenously and in a separate study was administered orally. The dose administered was 0.5 mg/kg orally or IV. Blood samples were safely taken and blood levels were measured to determine the half-life (T) of the drug and its bioavailability.
There were no apparent clinical side effects noted in any of the 20 birds used in this study. Bioavailability was 100% for intravenous administration and close to 100% bioavailable orally when given with food.
Dr. Wilson demonstrated that the T 1/2 of meloxicam given IV was 4 hours and given PO 14.7 hours. Interestingly, it appears the T 1/2 is inversely proportional to the weight; so the larger the bird, the shorter the T 1/2. In other words, larger birds may need to be dosed more frequently per day.
Conclusion:
Since NSAIDs are being used more and more in human and veterinary medicine. Dr. Nemetz has used Celecoxib and Meloxicam for a few years now and has had mixed results. This may not be the fault of the drug, but possibly dosing regimens, the individual species being treated, or inappropriate drug selection for a given inflammatory/pain process. Previous anecdotal dosing was suggested at 0.2-0.3 mg/kg PO q 12-24hr. This study suggests a higher dosage range of 0.5 -1.0 mg/kg PO q 12hr or 0.25 0.5 mg/kg IV q 4 hr based on the different T 1/2. Given orally with food also increases the drugs bioavailability. More work needs to be done as more options are being looked at to help our avian patients deal with inflammatory conditions caused by disease, trauma, or surgical events.