Pharmacokinetic behaviour of meloxicam in loggerhead sea turtle (Caretta caretta).

In rehabilitative medicine of sea turtles, traumatic lesions and infectious diseases are the more frequently encountered reasons to provide veterinary care to these animals. Trauma related emergencies (boat strikes, ingestion of fish hooks, entrapment in fish wires, etc.) require a surgical approach, and consequently a correct pain management. Data on reptile analgesia and pain management are scarce, both with NSAIDs and opioids, and totally lacking in sea turtles, so dosage regimens are generally extrapolated from other animal species, with consequent risks of clinical failure and damage to the animal. In order to avoid circumstances like these, preliminary data on the pharmacokinetic behavior of meloxicam in loggerhead sea turtle (Caretta caretta) are presented, in order to assert the possibility of its clinical use to provide pre- and post-surgical analgesia. Meloxicam has been chosen in spite of other NSAIDs because of its more selective anti-COX2 activity, and consequently expected lesser adverse side effects. 6 clinically health loggerhead turtles (courtesy of Lampedusa WWF Sea Turtles Rescue Center), 9.6-27.1 kg weight, were used. The animals were individually maintained in outdoor pools with continuous marine water flow, at 25-27°C and 35‰ salinity. The dose of 0.1 mg/kg of meloxicam was decided, so reducing the recommended dose used for dog and cat as no data are reported on the capacity of turtles to tolerate NSAIDs. Nevertheless, no adverse reaction was observed after the administration of the drug. Blood samples were collected from alternated cervical sinuses in lithium heparinized tubes. Meloxicam plasma concentrations were determined by DAD-HPLC. After the administration of a single i.m. dose, a very quick absorption rate has been noted, with time to peak concentration 0.79±0.28 h (mean ± s.e.), and peak concentrations 0.03±0,01 mg/ml. As pharmacodynamic and efficacy studies of meloxicam in reptiles have not been published, the minimum efficace concentration cannot be predicted, so further studies are requested to define the optimal dosage. A very fast disappearance of drug from vascular compartment was observed, with concentrations of drug below the quantitation limit (25 ng/ml) in 4.60±3.49 h, elimination half-life of 1.32±0.55 h, clearance of 4.32±1.19 L/h•kg, and apparent volume of distribution of 6.51±2.45 L/kg. These data are surprising enough, if compared with the ones reported in green iguana, where plasma concentrations resulted >0.1 mg/mL for up to 24 h, elimination half-life 9.93±4.92 h, clearance 0.037±0.016 L/h•kg, and apparent volume of distribution 0.46±0,12 L/kg following a single i.v. dose of 0.2 mg/kg. The large volume of distribution observed in loggerhead turtle suggests a wide tissue distribution, but nothing can be said on the persistence of drugs in tissues or real elimination of the drugs, so further studies are essential.