Bronx Zoo-based veterinarians have found a solution to the challenge of providing effective pain relief to some of their most difficult patients. Better than aspirin, a surgically implanted, capsule-sized pump delivers continuous pain relief while leopards, tigers, and lions recover from surgery.

A new study by Dr. John Sykes of the Wildlife Conservation Society’s Global Health Program, appearing in the August edition of the American Journal of Veterinary Research, features the benefits of using osmotic pumps in big cats. The study was funded by the Morris Animal Foundation. Drs. Sherry Cox and Edward C. Ramsay, the co-authors, carried out research at the University of Tennessee to test the device on house cats and evaluate the potential usage in their wild relatives. They found that the osmotic pumps delivered pain medications quickly, and that the medications also disappeared from the bloodstream quickly once the pump was removed. As a result of this work, the units have been used successfully on two leopards that underwent spay procedures at Tiger Haven, a big cat sanctuary in Tennessee.

Delivering pain relief to dogs, cats, or other pets after surgery is relatively easy compared with wild animals in zoos. While a vet can hold a small cat to give it a pill or injection, larger cats are too powerful to restrain easily. Transdermal patches sometimes used in domestic cats aren’t effective in wild cats, as they tend to remove them shortly after waking up from surgery. In addition, big cats will typically stop eating when in pain, eliminating the possibility of administering oral medication in tasty treats.

Osmotic pumps, on the other hand, provide veterinarians with a delivery device that cannot be removed by the animal patient and requires little handling of the animal. The pump—which ranges in size between 1.5 and 5.1 centimeters—can be implanted at the end of an operation and then removed weeks later with no other intervention needed.

The pump, which is placed just beneath the surface of the skin of the animal’s shoulder, contains the pain medication (in this case, fentanyl). The outer casing of the pump is permeable, and plasma from the animal enters the casing through osmosis. The medication then diffuses from a tiny bag through a small opening at the top of the pump. Since the flow of liquid out of the pump is constant, veterinarians control the rate of dosing through the concentration of the drug in the pump.

“This is a great example of how existing methodologies can be adapted for usage in wild cats in captive breeding programs,” said Dr. William Karesh, Director of WCS-Global Health. “It’s a win-win in that it reduces the effort by veterinarians to treat big cats while helping to reduce stress and thus speed healing in the cats themselves.”

Osmotic pumps can also deliver other medications. WCS veterinarians have successfully used the pumps to administer antibiotics to snakes and other animals at the Bronx Zoo.

Read the press release: Tiny Pump Means Pain Relief for Big Cats