Placebo may be an alternative to electrical nerve stimulation in pain relief

Transcutaneous electrical nerve stimulation has benefits that override those of analgesics in the treatment of chronic pain Its use tn clinical practice, either alone or in addition to mild analgesics, is becoming widespread.

The application of low voltage electrical stimulation often produces analgesia localised to the stimulated segments but pain usually returns when stimulation is halted. However, more intense stimulation produces prolonged analgesic effects and hence is the treatment of choice. Of the 3 types of intense stimulation, htgh frequency and acupuncture-like treatment have been found more effective than low frequency treatment.

Studies over the last decade have shown that endorphins are involved in the descendtng pain control pathways of intense transcutaneous electrical nerve sttmulatton, and that a specific optate antagontst, naloxone, reverses the effects of low frequency and acupuncture-like stimulatton but not of htgh frequency stimulation. The evidence thus indicates that the modes of action of the first 2 types of sttmulatton are comparable and involve endorphins.

While electncal nerve sttmulation has been cred1ted with less stde effects than analgestcs, and few contraindications, the placebo effects of thts mode of therapy have not been considered. Studies have shown that placebo can produce analgesia as well as other pharmacologtcal tratts such as drug dependence and 11 appears that the pathways tnvolved tn placebo analgesta are stmilar to those uttltsed by tntense electncal nerve sttmulatton. modulalton of the pa1n control system can produce prolonged patn reltef

It ts dtfftcult to compare the analges1c effects of placebo vs 1ntense electncal nerve sttmulatton because the ttngltng sensat1on assoc1ated wtth the latter 1s dtfftcult to tmitate wtth placebo Hence. crossover studtes are not double-bltnd but even so. tn non-crossover studtes. 11 has been suggested that paltents can focus thetr attentton on the ltngltng sensalton produced by electncal nerve sttmulation. resulltng tn modiftcatton of pa1n perceptton

Overall. placebo wtth sltmulator output shown on an oscilloscope screen iS as eifective as 1ntense electncal nerve stimulation and thus tis cltntcal use may be encouraged because it may be cheaper than electncal sttmulation. In addition, ' ... the physiological and biochemical effects of placebo demands that it no longer be considered an inert reference by which other therapies are gauged but recognised as a therapeutic tool in its own right'. Langley GB Sheppeard H New Zealand Med1cal J0111nal 100 215217.8 Apr 1987

4 INPHARMA" 2 May 1987 0156-2703!87!05020004/0$01.00/0 © ADIS Press