Efficacy of a Topical Palmitated Formulation of Capsaicin (Capsadyn®) In the Treatment of Diabetic Neuropathic Foot Pain

This is a double-blind, randomized, placebo-controlled trial with two arms to assess the pain-reducing effects of topical Capsadyn compared to a placebo (carrier cream). At the appointment/recruitment visit, patients will receive standard of care as determined by their clinician. At the first visit, participants opting into the trial will not receive any new medications designed for producing pain relief alongside the Test Article but will continue medications taken before entry to the study, if use history is stable, or medications not specifically designed for pain reduction. Both the clinician administering the Test Article and the participant will be blinded to Test Article, or unaware of whether it is Capsadyn or placebo.

A Test article can be administered to either a unilateral area, or bilateral painful areas. Test Article should be administered over the complete painful area. Test Articles will be packaged in coded, white-labeled one-ounce plastic jars, marked only with a code indicating Capsadyn or placebo, and sent to Carilion Pharmacy for distribution to healthcare providers. The pharmacy will quarantine the Test Articles and randomize Test Article scheduling between the two arms. The participant population will be scheduled for an even split between the two study arms. With the recruitment of 40 participants (20 per group), an interim look at the data will be done to assess participant compliance with instructions, general progress of the study and to troubleshoot any issues that may have arisen.

Inclusion criteria

• At least 3 toes per foot
• Have otherwise intact feet.
• Absence of any eczema, hyperkeratosis, scleroderma, or other dermatological conditions afflicting the area of Test Article administration that may interfere with absorption, particularly hyperhidrosis.
• Must agree to apply the Test Article to painful areas of feet as directed by research personnel.
• Must agree to apply the Test Article to feet as instructed 2x per day.
• Must wait 60 minutes after each application of Test Article before filling out NRS forms.
• Unless burning is encountered soon after application, the participant must wait at least 60 minutes before washing feet after application of Test Article.
• All participants must be willing to use Test Articles blinded.

Exclusion criteria

• Younger than 25 and older than 75 years of age
• Any dermatological condition(s) with the potential to disrupt skin integrity or alter sensory function of the feet.
• Any open wounds, skin ulceration, infection, skin irritation (e.g., poison oak), history of eczema, trauma or burn (including sunburn) affecting the feet within 30 days.
• Any recent medical history of surgery affecting the feet.
• Unless part of a stable continuum of substance use prior to start of study, the use of any topical medication products on feet, including holistic formulations, patch or herbal products, cannabinoid products, prescription or over the-counter (OTC) analgesic creams/lotions/patches/gels, nonsteroidal anti-inflammatory drugs, acetaminophen, counterirritants, local anesthetics, or steroids is prohibited.
• Current substance abuse.
• History of hypersensitivity or allergy to chili peppers, coconut oil, Shea butter, or sunflower seed oil.
• Except for interventions for mobility, (e.g., physical therapy, exercise, grounding) no concurrent foot therapy for pain that may interfere with NRS evaluations is permitted (e.g., massage, electrophoresis, red light, etc.).
• No concurrent enrollment in another clinical trial.