NIH expands RTX to dogs

Dr. Kory McHenry, former fellow at NIH (NINDS/NIDCR) pain group under Michael Iadarola and contributor to painonline has written here about resiniferatoxin. (see his prior articles). Now the RTX experiments have been conducted in dogs.


Although of proven efficacy in rats, the NIH has now tested resiniferatoxin (RTX) in dogs. Their model was cancer pain, with the canines unwilling to put weight on the affected limb. As might be expected, flow through the TRPV-1 channel causes burning briefly until the pain fibers are killed. Placing the animals under anesthesia to cover the very brief time necessary for RTX to work, the experiments demonstrated the injection of RTX into the spinal canal was effective at relieving the pain of an affected limb.

As you already know from previous posts, buildup of calcium (CA2+) such as comes from any interference with sodium-calcium exchange at the membrane of a neuron CAUSES pain from calcium buildup. RTX pours so much Calcium through the TRPV-1 receptor that the cell bursts (under the microscope it looks as if the membranes inside the cell are disintegrating) and dies. The process takes less than a minute.

RTX is like a powerful cousin of capsaicin which comes from chili peppers. RTX comes from a Moroccan cactus. In antiquity the plant was known as Euphorbia and was used by Mark Anthony and others. After the RTX is injected into the cords, the dogs awake in a sweat, just as people might sweat after consuming chili peppers. So far, this is the only reported side effect. The drug is selective for pain neurons. Although the NIH spent two million dollars seed money to collect and concentrate the drug, so far no drug company has stepped forward to bear the expense of human trials, because the market is said to be so small. NIH estimates only 50 to 100 thousand people would be candidates. Because it reaches morphine insensitive pain, it seems likely the FDA would grant orphan drug status which should shorten the time required to bring the drug to the public.

The main researchers include Michael Iadarola and Andrew Mannes. For us, there are no bigger heroes than these scientists conducting pain research. They spend their lives quietly benefitting mankind.