The efficacy of acupuncture in human pain models: a randomized, controlled, double-blinded study

Acupuncture is frequently used to treat pain, although data supporting the analgesic efficacy from placebo-controlled studies is sparse. In order to get evidence for acupuncture analgesia we performed a study with 2 well-recognized experimental human pain models - the cold-pressor (CP) test and intradermal capsaicin injection. Fifty healthy men were included. Our study compared Traditional Chinese Medicine-based acupuncture to sham acupuncture with Streitberger placebo needles in a randomized, controlled, double-blinded trial. The primary endpoint was the reduction of mean pain intensity during 3minutes of CP test or of mean pain intensity within 10minutes after capsaicin injection. Secondary parameters were defined to substantiate the findings. To ensure comparability, somatosensory (measured by quantitative sensory testing) and psychological parameters were investigated and found to be the same in both groups. Analyses (repeated-measures analyses of variance) showed a significant (P=0.009) but clinically questionable pain reduction in the verum group for capsaicin-induced pain, which was mainly driven by an effect of Traditional Chinese Medicine acupuncture on small pain ratings (max. reduction from 7/100 rating at baseline to 2.5/100 at intervention). Neither pin-prick hyperalgesia, nor allodynia, nor neurogenic flare associated with capsaicin injection, nor pain ratings during the CP test, were significantly different between groups. In addition, there was no placebo response. Attitude towards acupuncture and partial unblinding did not affect the results. We conclude that acupuncture on predefined points has a minor effect on experimental pain in healthy subjects.