Abstract

One of the challenges of managing the health of any aquatic animal collection involves attending to medical conditions that may reasonably be expected to have a pain component. In some cases, non-medical measures (e.g., behavioral conditioning) may be sufficient to address mild discomfort. It is common practice to utilize conclusions drawn from pharmacologic investigations in other (frequently domestic) animal species, and adapt them for use in the species in question. Anecdotal reports of a drug's use at other institutions, successfully or otherwise, can also provide useful information, particularly for newer drugs, or those which have a paucity of documented use in non-domestic species. This report briefly details the use of several of these analgesic and/or sedative drugs in marine mammal species at the New York Aquarium.

Using these drugs and protocols at the New York Aquarium, variable degrees of analgesia were subjectively achieved in Pacific walrus (Odobenus rosmarus), California sea lion (Zalophus californianus), Northern fur seal (Callorhinus ursinus), and Southern sea otter (Enhydra lutris). However, of equal if not greater importance, several of these protocols resulted in mild relaxation to moderate sedation, permitting physical examination and mildly invasive treatment procedures. Having a safe, reliable, and repeatable method of achieving sedation in animals such as these can be a valuable diagnostic and treatment tool, avoiding the need to resort to full anesthesia, or subjecting a potentially compromised animal to manual restraint. The following drugs were used safely at the dosages reported.

Medetomidine has been used specifically for analgesia and mild sedation to disrupt the pain cycle in a Pacific walrus at a dosage of 0.01 mg/kg intramuscularly alone, and in conjunction with buprenorphine at 1 to 2 µg/kg intramuscularly. This was effective for up to 12 hours.

Buprenorphine has been used in Pacific walrus (n=2) at dosages ranging from 1 to 5 µg/kg intramuscularly and via mucosal application once and twice daily; in California sea lion (n=2) at dosages ranging from 9 to 10 µg/kg intramuscularly once and twice daily; in Northern Fur seal (n=2) at dosages ranging from 3 to 20 µg/kg intramuscularly once and twice daily; and in Southern sea otter (n=1) at dosages ranging from 3 to 12 µg/kg intramuscularly once and twice daily. This drug was used alone, and in combination with dexamethasone, prednisone, flunixin, carprofen, meloxicam, tramadol, and gabapentin. In each species, no or minimal sedation was seen at lower dosages, while mild to moderate sedation was generally seen at higher dosages.

Diazepam has effectively been used orally to achieve relaxation/anxiolysis in Pacific walrus (n=2) at a dosage of approximately 0.3 mg/kg; in California sea lion (n=3) at dosages ranging from 0.1 to 0.5 mg/kg; and in Southern sea otter (n=1) at a dosage of 1.6 mg/kg. However, in one California sea lion, the animal's behavior was described as being unpredictable at the higher dosage.

In one California sea lion, good sedation requiring no supplementation was obtained serially over consecutive days with the following two-drug protocols: 1) buprenorphine 5 µg/kg IM/diazepam 0.25 mg/kg IM; 2) diazepam 0.25 mg/kg IM followed by butorphanol 0.1 mg/kg IV; 3) midazolam 0.5 mg/kg IM followed by butorphanol 0.15 mg/kg IM.

Tramadol has been used orally for analgesia in Pacific walrus (n=2) at dosages ranging from 1.0 to 3.0 mg/kg once and twice daily; in California sea lion (n=1) at dosages ranging from 0.4 to 2.1 mg/kg once and twice daily; in Northern Fur seal (n=4) at dosages ranging from 1.0 to 3.6 mg/kg once and twice daily. This drug was not used in Southern sea otters. It has been used alone, and in combination with prednisone, celecoxib, carprofen, flunixin, buprenorphine, and gabapentin.

Gabapentin has been used orally in cases where neurogenic pain was suspected in Pacific walrus (n=1) at a dosage of 1.1 mg/kg twice daily; in California sea lion (n=1) at dosages ranging from 2.3 to 7.4 mg/kg twice daily; in Northern Fur seal (n=3) at dosages ranging from 4.3 to 12.0 mg/kg twice daily; and in Southern sea otter (n=1) at dosages ranging from 4.5 to 8.2 mg/kg three times daily. This drug was used alone, and in combination with prednisone, flunixin, butorphanol, tramadol, and buprenorphine.

Acknowledgements

Acknowledgement and appreciation are extended to the Animal Husbandry staff at the New York Aquarium, to the curator of Aquatic Animal Laboratory Services Catherine McClave and technicians Patricia Toledo and Marisa Meilak, and to the veterinary clinicians at the Wildlife Health Center, without whose dedication and expertise these efforts would not be possible.