DOUBLE-BLIND, PLACEBO-CONTROLLED STUDY OF THE APPLICATION OF CAPSAICIN CREAM IN CHRONIC DISTAL PAINFUL POLYNEUROPATHY

We have completed a 12-week double-blind, placebo-controlled randomize d study on the efficacy of the application of capsaicin (CAPS) cream ( 0.075%) in the treatment of chronic distal painful polyneuropathy. For ty patients were enrolled and 39 completed the study. The 2 limbs were randomly assigned to CAPS or placebo (PLAC). The cream was applied 4 times a day. The first tube contained the active PLAC, methyl nicotina te. In the final 4 weeks (single-blind wash-out phase), PLAC was admin istered bilaterally. Efficacy was evaluated using the following scales : (1) investigator global (2) patient global, (3) visual analog (VAS) of pain severity, (4) VAS of pain relief, (5) activities of daily livi ng, and (6) allodynia. Patients were examined at onset and at monthly intervals using a neurologic disability scale, nerve conduction studie s, computer-assisted sensory examination for vibration and thermal coo ling and warming, QSART (quantitative sudomotor axon reflex test) and quantitative flare response. There was no statistical evidence of effi cacy of CAPS cream over PLAC for any of the pain indices. At early tim e points (1-4 weeks), there were a small number of indices that favore d the PLAC. The percent of limbs that improved on the investigator's g lobal scale were 51.3 vs. 53.8 at 4 weeks, 56.4 vs. 64.1 at 8 weeks an d 59 vs. 66.7 at 12 weeks for CAPS vs. PLAC; no statistically signific ant difference was found. All the safety indices showed no difference between sides. We interpret the early hyperalgesia on the CAPS side as being responsible for the better performance of PLAC at early time po ints. The large percentage of limbs that improved may be a pronounced PLAC response.