By Ryan DuBosar
Before prescribing chronic pain medications for older patients, Erin E. Krebs, MD, MPH, FACP, first considers both their pain and the risks of treatment on a spectrum.
"Yes, chronic pain is extremely common," said Dr. Krebs, chief of general internal medicine at the Minneapolis VA Health Care System and a professor of medicine at the University of Minnesota Medical School. "For many, pain is a manageable symptom. For some, pain is a debilitating disease. And for a lot of people, it's somewhere in between. So it is important to figure out where your patient is."
Dr. Krebs outlined drug therapy options for chronic pain from least harmful to most harmful. Although the risk of harm is low with capsaicin, its benefits are small for knee osteoarthritis, and it's not effective for peripheral neuropathy. Capsaicin works best for small joints, is not suitable for all locations on the body, and must be applied frequently.
"So you've got to keep putting it on at least every six to eight hours," she tells patients, adding that the side effects are minor: "You're not going to get anything but burning."
Similarly, lidocaine and topical salicylates have little evidence of effectiveness, but they are very safe. When advising use of lidocaine patches, Dr. Krebs tells patients to take 12-hour breaks to avoid tachyphylaxis.*
"Many of my older patients have felt that they are getting benefit from these drugs and like them," she said. "I frankly think there's very little downside to trying this for a lot of patients."
Next up, going from safest to riskiest, is acetaminophen, which Dr. Krebs called "a bit of a conundrum for me." The evidence for its effectiveness is pretty poor, but it's considered generally safe at the recommended daily dose for most people, including older adults, with the caveat that its common presence in combination products increases the risk of overdose toxicity.
NSAIDs carry clear evidence of small to moderate benefits for low back pain, osteoarthritis, and inflammatory arthritis. "The good news is that all NSAIDs seem to have similar efficacy, including the topical ones," Dr. Krebs said. "But of course, everybody knows, oral NSAIDs have important gastrointestinal, renal, [and] cardiovascular risks, especially for older adults, and especially for those with other medical conditions."
She next discussed antidepressants and anticonvulsants as a group because they have similar indications and similar adverse effects. Duloxetine is recommended in all the guidelines, with clear evidence of small benefits for back pain, arthritis, peripheral neuropathy, and fibromyalgia. But the drug class poses important psychomotor and cognitive risks in older adults.
"[I]f you're thinking about these drugs, shared decision making is important to talk about risks and benefits," she said. "You really want to see benefits to continue with these. They should not just be continued forever. I think these are some of the most overused medications we have, primarily because they get started and not stopped."
Next, tramadol got its own slot, between antidepressants and opioids, because it has mixed mechanisms of serotonin and norepinephrine reuptake inhibition. Evidence for tramadol's effectiveness on low back pain, osteoarthritis, and fibromyalgia is better than that for a lot of antidepressants and opioids. But it can also have psychomotor and cognitive effects in older adults. Clinicians should assume the risks of dependence, addiction, and overdose seen with opioids apply to tramadol as well, she said.
"I am not a big fan of tramadol," Dr. Krebs said, calling the drug "the worst of both worlds."
Opioids took the last spot on the list, as they are the least safe and not recommended by guidelines, although they do have small benefits in terms of pain compared to placebo. Trials generally exaggerate the benefits of opioids, Dr. Krebs said, and tolerance develops very rapidly, quickly counteracting analgesic benefits.
"So they may be helpful in the short term, but they are unlikely to really have efficacy that persists over time in chronic pain, and what we care about in chronic pain is the long term," she said. ■
*This sentence was updated on 4/29/23 to change "cataplexy" to "tachyphylaxis."