title: Reduced analgesic effect of acupuncture-like TENS but not conventional TENS in opioid-treated patients.
abstract: Evidence from recent animal studies indicates that the analgesic effect of low-frequency transcutaneous electrical nerve stimulation (TENS) is reduced in opioid-tolerant animals. The aim of the present study was to compare the analgesic effect of conventional (high frequency) and acupuncture-like (low frequency) TENS between a group of opioid-treated patients and a group of opioid-naive patients in order to determine if this cross-tolerance effect is also present in humans. Twenty-three chronic pain patients (11 who took opioids and 12 who did not) participated in the study. Participants were assigned in a randomized crossover design to receive alternately conventional and acupuncture-like TENS. There was a significant reduction in pain during and after conventional TENS when compared to baseline for both the opioid and nonopioid group (P < .01). For acupuncture-like TENS however, the analgesic effect of TENS was only observed in the nonopioid group (P < .01), with opioid-treated patients showing no change in pain scores during and after TENS when compared to baseline (P > .09). The reduced analgesic effect of acupuncture-like TENS in opioid-treated patients is coherent with previous animal studies and suggests that conventional TENS should be preferred in patients taking opioids on a regular basis.
  
  
  CONCLUSIONS
  This study shows that patients taking opioids on a regular basis are less susceptible to benefit from acupuncture-like TENS. This phenomenon is probably attributable to the fact that the analgesia induced by acupuncture-like TENS and opioids are mediated by the same receptors (ie, μ opioid receptors).
authors.affiliation: Université de Sherbrooke, Faculté de médecine, Sherbrooke, Québec, Canada.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Léonard
authors.forename: Christian
authors.initials: C
authors.lastname: Cloutier
authors.forename: Serge
authors.initials: S
authors.lastname: Marchand
mesh_terms: D015667:Acupuncture Analgesia / Q000379:methods* / Q000639:trends; D000328:Adult; D000368:Aged; D000701:Analgesics, Opioid / Q000009:adverse effects*; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care / Q000379:methods; D010148:Intractable Pain / Q000209:etiology / Q000628:therapy*; D004561:Transcutaneous Electric Nerve Stimulation / Q000379:methods* / Q000639:trends; D055815:Young Adult
chemical_list: D000701:Analgesics, Opioid