Topical creams likely ineffective in treating localized chronic pain

1. In a randomized controlled trial, researchers found that topical analgesic creams were ineffective in treating localized chronic pain.

2. Compared to the placebo, there were no improvements in average pain score, maximum pain score, patient satisfaction, or physical impairment.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Around 100 million Americans suffer from chronic pain, but many find oral analgesics to be ineffective or side effect-ridden.  Active service members have even fewer options, since many cannot take opioids while on duty out of concern for cognitive impairment or addiction.  Topical analgesic creams represent one attractive alternative.  This study evaluated the efficacy of topical creams in treating neuropathic pain, nociceptive pain, and mixed pain in patients at an academic military treatment facility.  For each class of pain, accepted systemic therapies were compounded and adapted for dermal application, with closely matched placebo controls.  After one month of regular treatment, patients in both treatment and control groups reported improvements in their pain score.  However, there was no significant difference between treatment and placebo for any type of pain, or for all patients in aggregate.  There was also no evidence of functional improvement or patient satisfaction.  Those patients who did have positive outcomes at one month were followed for another 2 months, but there was still no significant difference between treatment and placebo.  Other recent studies have suggested that topical creams are modestly effective, at best, but this study is unique in its thorough double-blind format and military-focused population.  However, these traits also underlined many of the study’s weaknesses.  The study did not evaluate capsaicin – one of the most promising topical candidates – because of its capacity to cause a distinctive burning sensation upon application that would invalidate blinding.  Furthermore, the focus on active military members biased the trial towards conditions affecting younger patients, which may not be representative of the average patient with chronic pain.

 Click to read the study, published today in Annals of Internal Medicine

Relevant Reading: Topical lidocaine for neuropathic pain in adults

In-Depth [randomized controlled trial]: This study evaluated the efficacy of compounded topical creams for managing chronic pain at an urban military treatment facility that serves service members, government officials, and their families.  A total of 399 patients were recruited, including 133 with neuropathic pain, 133 with nociceptive pain, and 133 with mixed-type pain.  Patients with neuropathic pain received either placebo or a cream containing ketamine, gabapentin, clonidine, and lidocaine.  Patients with nociceptive pain received either a placebo or a cream with ketoprofen, baclofen, cyclobenzaprine, and lidocaine.  For mixed pain disorders, patients received a subset of both prior lists.  The dosage was standardized based on the size of the affected area, and compliance was self-reported.  In order to determine drug efficacy, patients recorded their average and peak pain scores twice daily, on a scale of 1 to 10.  They were also interviewed by a blinded investigator to assess their emotional health and physical function, as well as treatment satisfaction on a scale of 1 to 5.  A “positive outcome” was defined as an average pain score reduction of 2 or more points, coupled with a satisfaction score of 3 or above.  After one month of treatment, there was no statistically or clinically significant difference in the rate of positive outcomes between the control and treatment for any of the pain subtypes.  For the amalgamation of all treatment and placebo groups, the mean difference was only -0.3 points (CI₉₅, -0.6 to 0.1).  There was also no improvement in standardized markers of mental health or physical disability.  Only about a third of patients correctly guessed their treatment vs placebo assignment.

Image: PD

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