The anticipated pain of surgery, and even post-operative pain, is keeping a lot of patients from going for that much needed treatment. Although anesthesia has been effective for keeping a patient asleep, immobile, and out of pain during complicated surgeries — it can hardly prevent pain from recurring once the patient wakes up.
Due to the limitations of anesthesia, the medical and research community has been looking for a suitable substitute or alternative. Recently, scientists have made experiments on substances that are used to make hot sauce. Surgeons have tried to use the chemical that gives chili peppers their “fire” as an experimental anesthetic by directly pouring the said substance into open wounds during knee replacement and a few other highly painful operations. The experiments made use of an ultra-purified version of capsaicin to avoid infection. Volunteers were under placed under anesthesia so that they don’t feel the initial burn.
Treating surgically exposed nerves with a high dose of capsaicin will numb them for weeks, so that patients suffer less pain and require fewer narcotic painkillers as they heal. According to Dr. Eske Aasvang, a pain specialist in Denmark who is testing the substance, “We wanted to exploit this numbness.”
For centuries, chili peppers have been part of folk remedy and heat-inducing capsaicin creams are a familiar drugstore cure for muscle spasms. Today, however, the spice is also commercially “hot” due to research showing how capsaicin targets key pain-sensing cells in a unique way. Aside from California-based Anesiva Inc.’s attempt to harness that burn for more focused pain relief, Harvard University researchers are also mixing capsaicin with another anesthetic drug in hopes of developing epidurals that would not confine women to bed during childbirth, or dental injections that don’t numb the whole mouth. At the National Institutes of Health, scientists hope that by early next year, they can begin testing in advanced cancer patients a capsaicin variant that is 1,000 times more potent, to see if it can zap their intractable pain.
Nerve cells that sense a type of long-term throbbing pain contain a receptor, called TRPV1. Capsaicin binds to this receptor and works to produce a painkilling action on specific pain-receiving fibers.
These so-called C neurons also sense heat; thus capsaicin’s burn. But when TRPV1 opens, it lets extra calcium inside the cells until the nerves become overloaded and shut down. That’s the numbness. “It just required a new outlook about … stimulation of this receptor to turn those cellular discoveries into a therapy hunt,” says NIH’s Dr. Michael Iadarola.
In a meeting of the American Society of Anesthesiologists, Aasvang reported that forty one men were tested and underwent open hernia repair. Capsaicin recipients experienced significantly less pain in the first three days after surgery. Another U.S. study of 50 knee replacements, half were treated with capsaicin who used less morphine in the 48 hours after surgery and experienced less pain for two weeks. Several on-going studies are experimenting with larger doses in more patients to find out whether the effect is real.
“There’s a huge need for better surgical pain relief,” said Dr. Eugene Viscusi, Director of Acute Pain Management at Thomas Jefferson University in Philadelphia, Pennsylvania, one of the test sites. “Morphine and its relatives, so-called opioid painkillers, are surgery’s standby. While they’re crucial drugs, they have serious side effects that limit their use.”