Topical capsaicin in painful diabetic neuropathy. Effect on sensory function.

OBJECTIVE: To examine the effect of capsaicin on sensory function in painful diabetic neuropathy. RESEARCH DESIGN AND METHODS: We examined the effects of topical 0.075% capsaicin cream on thermal and vibration thresholds in 22 subjects with painful diabetic neuropathy who participated in a double-blind vehicle-controlled therapeutic trial. RESULTS: After 8 wk of use, there was no significant change in warm and vibration thresholds, but the cold threshold was significantly reduced by capsaicin and vehicle creams to an equal degree. In fewer subjects who used capsaicin cream in an open-label study, there was no significant effect on sensory thresholds after up to 32 wk of use. CONCLUSIONS: Although our results and those of others show no adverse effects of topical 0.075% capsaicin on human sensory function, even in subjects with preexisting neuropathic sensory impairment, the small number of subjects tested does not justify an inferential statement on safety. Further studies in more subjects are warranted to ensure the long-term safety of capsaicin for pain relief in humans.

Topical capsaicin in painful diabetic neuropathy. Controlled study with long-term follow-up.

OBJECTIVE: We conducted an 8-wk controlled study with topical 0.075% capsaicin in subjects with chronic severe painful diabetic neuropathy who were unresponsive or intolerant to conventional therapy. Capsaicin is an alkaloid found in capsicum peppers and produces desensitization to noxious thermal, chemical, and mechanical stimuli when applied topically. RESEARCH DESIGN AND METHODS: In 22 randomly assigned subjects, either capsaicin or vehicle cream was applied to painful areas 4 times/day. Pain measurements were recorded at baseline and at 2-wk intervals for 8 wk. RESULTS: Capsaicin treatment was more beneficial than vehicle treatment in the overall clinical improvement of pain status, as measured by physician's global evaluation (P = 0.038) and by a categorical pain severity scale (P = 0.057). Decrease in mean pain intensity by a visual analogue scale was 16% in capsaicin-treated and 4.1% in vehicle-treated subjects. Mean pain relief on visual analogue scale was 44.6 and 23.2%, respectively. In a follow-up open-label study, approximately 50% of subjects reported improved pain control or were cured, and 25% each were unchanged or worse. A burning sensation at the application site was noted by some subjects but both its magnitude and duration decreased with time. CONCLUSIONS: Results from this preliminary study suggest that topical 0.075% capsaicin may be of value in subjects with diabetic neuropathy and intractable pain.