How do you differentiate between these types of pain in your study?
We phenotype people by asking them a number of questions. We also do brain imaging, look at their back with MRI, test biomechanics, and then give them four different treatments that we know work in groups of people with low back pain.
We think one of the first parts of the phenotype is, do they have pain just in their back? Or do they have pain in their back plus a lot of other body regions? Because the more body regions that people have pain in, the more likely it is that this is an amplifier problem rather than a guitar problem.
Treatments like physical therapy, surgery, and injections are going to work better for people in whom the pain is a guitar problem rather than an amplifier problem. And drugs like duloxetine, which works in the brain, and cognitive-behavioral therapy are going to work a lot better in the people with pain in multiple sites besides the back.
To pick up on your metaphor, do any symptoms help clinicians differentiate between the guitar and the amplifier?
Sleep problems, fatigue, memory problems, and mood problems are common in patients with chronic pain and are more common with amplifier pain. Because again, those are all central nervous system problems. And so we see that the people that have anxiety, depression, and a lot of distress are more likely to have this kind of pain.
Does medical imaging help?
There’s a terrible relationship between what you see on an MRI of the back and whether someone has pain or how severe the pain is going to be. There’s always going to be individuals that have a lot of anatomic damage who don’t have any pain because they happen to be on the other end of the continuum from fibromyalgia; they’re actually pain-insensitive people.
What are your thoughts about ketamine as a possible treatment for chronic pain?
I have a mentee who’s doing a ketamine trial. We’re doing psilocybin trials in patients with fibromyalgia. Ketamine is such a dirty drug; it has so many different mechanisms of action. It does have some psychedelic effects, but it also is an NMDA blocker. It really has so many different effects.
I think it’s being thrown around like water in settings where we don’t yet know it to be efficacious. Even the data in treatment-refractory depression are pretty weak, but we’re so desperate to do something for those patients. If you’re trying to harness the psychedelic properties of ketamine, I think there’s other psychedelics that are a lot more interesting, which is why we’re using psilocybin for a subset of patients. Most of us in the pain field think that the psychedelics will work best for the people with chronic pain who have a lot of comorbid psychiatric illness, especially the ones with a lot of trauma. These drugs will allow us therapeutically to get at a lot of these patients with the side-by-side psychotherapy that’s being done as people are getting care in the medicalized setting.
Dr. Clauw reported conflicts of interest with Pfizer, Tonix, Theravance, Zynerba, Samumed, Aptinyx, Daiichi Sankyo, Intec, Regeneron, Teva, Lundbeck, Virios, and Cerephex.
A version of this article first appeared on Medscape.com.