ILLUSTRATIVE CASE
A 23-year-old man with no significant past medical history presents to an urgent care center after a fall on his right arm while playing football. He reports a pain level of 6 using the visual analog scale (VAS). Physical exam reveals minor erythema and edema of his forearm with pain to palpation. Range of motion, strength, and sensation are intact. No lacerations are present. His vital signs are normal. No fracture is found on imaging. The physician decides that treatment with a topical analgesic is reasonable for this uncomplicated contusion of the right forearm. Is there a role for topical capsaicin in the treatment of this patient’s pain?
Topical nonsteroidal anti-inflammatory drugs (NSAIDs) are effective for the treatment of acute non–low back pain musculoskeletal injuries.2 They are generally well tolerated and just as effective as oral NSAIDS or acetaminophen for localized injuries. Their ubiquitous availability, affordability, and low adverse effect profile make them an attractive first-line treatment option for acute musculoskeletal pain.
Capsaicin, a topical agent derived from a genus of red peppers, has been used for the treatment of neuropathic and chronic pain via its interactions with substance P, transient receptor potential vanilloid subtype 1 (TRPV1), and nociceptive nerve fibers.3,4 It has demonstrated effectiveness in the management of diabetic neuropathy, knee osteoarthritis, and postherpetic neuralgia, as well as various causes of pruritus.5,6
Although many studies have compared oral and topical NSAIDs, opiates, and acetaminophen, few studies have directly compared topical NSAIDs and capsaicin. This study compared the topical NSAID piroxicam with topical capsaicin.
STUDY SUMMARY
Topical capsaicin demonstrated superior pain reduction
This prospective, double-blind RCT compared the efficacy of topical capsaicin vs topical piroxicam for the treatment of acute pain following upper extremity blunt trauma. Patients (ages ≥ 18 years) who presented to a Turkish emergency department within 2 hours of upper extremity injury were randomized to receive either 0.05% capsaicin gel (n = 69) or 0.5% piroxicam gel (n = 67). Patients reported level 5 or higher pain on the VAS. Those with fractures, dislocations, skin disruption, or other trauma were excluded. Age, gender, pain duration, and mechanism of injury did not differ significantly between study groups.1
Blinding was ensured by placing the gels in opaque containers containing 30 mg of either capsaicin or piroxicam and dyeing the medicine with red and yellow food coloring. A thin layer of medication was applied to an area no larger than 5 × 5 cm on the upper extremity and rubbed for 1 minute. Patients were observed in the emergency department for 2 hours and discharged with instructions to apply the medication 3 times daily for 72 hours.
The investigators measured pain using VAS scores at 1 hour, 2 hours, 24 hours, and 72 hours after treatment. Topical capsaicin was superior to topical piroxicam at achieving both primary outcomes: a VAS score of ≤ 4 (85.5% vs 50.7%; number needed to treat [NNT] = 2.9; P < .001) and a > 50% reduction in VAS score (87% vs 62.7%; NNT = 4.1; P < .01) at the end of treatment.1 (These outcomes were based on earlier determinations of the minimal clinically important difference.7,8)
Additionally, capsaicin was more effective than piroxicam at each time interval. This difference was most pronounced at 72 hours, with a mean difference of delta VAS scores of 1.53 (95% CI, 0.85-2.221) and a mean percentage of the reduction in VAS scores of 19.7% (95% CI, 12.4%-27.2%) (P < .001).1
