New animal research published in the Journal of Clinical Investigation shows that veterinarians and human physicians may be able to manage chronic pain by removing nerve cells from the nervous system. Originally tested on eight dogs with severe osteoarthritis and cancer pain, the process of eliminating C-fibers from the spinal fluid has proved to be successful and has caused no side effects, said Dorothy Brown, DVM, DACVS, assistant professor at the University of Pennsylvania. She has used the procedure in at least 20 cancer dogs and expects to submit another research paper for publication this fall.

Brown completed the first procedure in June 2002. She had been recruited by researchers from the National Institutes of Health who were seeking alternatives to non-steroidal, anti-inflammatory drugs (NSAIDs) and opiates to alleviate pain in cancer patients. Both options can cause bowel and bladder dysfunction when prescribed in high doses, Brown said.

The procedure tested by Brown and NIH researchers uses the drug resiniferatoxin (RTX), which has been used for years as a topical cream to alleviate pain at nerve endings. Because it had proven to be effective as a topical cream, the researchers wanted to see what RTX would do if it were injected “into the heart of the matter,” Brown said.

“Theoretically, it would delete the cell body so that the nerve wouldn’t regenerate,” she said. After blood work analyses and general anesthesia, RTX was injected in the dogs’ cerebral spinal fluid. The process took about an hour, and dogs were monitored overnight. 

Researchers saw a positive effect in all the dogs after a few days that lasted to the end of their lives. Brown said that after treatment the dogs lived for two weeks to nine months without pain. Risks include the administration of general anesthesia and the fact that the deletion of C-fiber nerve cells also eliminates a dog’s ability to feel heat.