Results of a double-blind, randomized controlled trial showed there were no differences in the mean reduction in average pain scores between treatment and control groups for patients with neuropathic pain, nociceptive pain, or mixed localized chronic pain.
“Compounded pain creams were not better than placebo creams, and their higher costs compared with approved compounds should curtail use,” study investigators led by Steven P. Cohen, MD, director of pain research at Walter Reed National Military Medical Center and professor of anesthesiology and critical care medicine at the Johns Hopkins School of Medicine, write.
High Cost an Issue
“Previous research clearly shows that some of the agents like lidocaine for non-neuropathic nerve pain and the nonsteroidal anti-inflammatory drugs like diclofenac are effective for non-neuropathic pain. The evidence for the other drugs was either just anecdotal or negative, and it also lacked an effectual basis,” Cohen told Medscape Medical News.
Many compounded pain creams include drugs like ketamine, baclofen, cyclobenzaprine, and lidocaine. However, until now, little work has been done to evaluate their effectiveness at providing significant neuropathic pain relief, he added.
To determine the efficacy of compounded creams for chronic pain the investigators conducted a double-blind randomized parallel study that included 399 patients with localized pain classified by each patient’s treating physician as neuropathic (n = 133), nociceptive (n = 133), or mixed (n = 133). Pain was categorized by a board-certified pain medicine treating physician.
To be included, participants had to have localized pain, including in the face, back or buttocks, neck, abdomen, chest, groin, or up to two extremities.
They were also required to have an average pain score of four or greater on a 10-point numerical rating scale during the preceding week, and have symptoms lasting more than 6 weeks.
No Impact on CNS
Pain cream formulations were selected on the basis of accepted systemic indications for neuropathic and nociceptive pain. Following treatment, participants recorded their average and worst pain scores twice each day in a pain diary, which researchers then used to calculate outcomes.
These results were not surprising, said Cohen.
“Supposedly, these compounded pain creams are great because they’re opioid-bearing but don’t have side effects. But the reason they don’t have side effects is because they don’t make it into the central nervous system at therapeutic levels. In other words, you can’t have your cake and eat it too.”
The investigators note that the study had two significant limitations.
Second, while investigators included some topical analgesics shown to provide benefit, they did not include capsaicin, which is FDA-approved for both neuropathic and nociceptive pain, or amitriptyline, which is not FDA-approved for chronic pain and has not been shown to be effective topically.
Commenting on the findings for Medscape Medical News, Kaliq Chang, MD, an interventional pain management specialist at the Atlantic Spine Center, who was not involved in the study, said compounded creams are “becoming increasingly prevalent in pain management practice and are heavily marketed by compounding pharmacies as they are very profitable drugs to produce.”
“However, there are not many well-designed studies looking at the efficacy of these treatments. The [study] results show there was no statistically significant improvement of pain with using three different compound creams at 1-month or 3-month follow-up.
“There was also no statistically significant difference between each compound pain cream and placebo cream. I agree with the conclusions of the authors that, perhaps, the high costs of these compound creams don’t justify the use of these treatments,” he said.
Study coauthor Mark C. Bicket, MD, reports grants from the Foundation for Anesthesia Education and Research during the conduct of the study and personal fees from Axial Healthcare outside the submitted work. Cohen reports personal fees from Semnur; grants from SPR Therapeutics; grants and personal fees from Avanos; and advisory board membership at Semnur, Boston Scientific, and Medtronic, outside the submitted work. Chang and study couthors not named here have disclosed no relevant financial relationships.
Ann Intern Med. Published online February 4, 2019. Full text