The reports on pain perception among former
heroin addicts receiving
methadone maintenance treatment (
MMT) vary with regard to
pain and intolerance threshold, and perception of suprathreshold stimuli has not been previously evaluated. Our aim was to systematically assess perception of threshold and suprathreshold noxious and innocuous stimuli with special attention to the effect of
MMT dose and the presence of
chronic pain. Noxious and innocuous, thermal and mechanical thresholds and ratings of suprathreshold heat-
pain stimuli were measured among 31
MMT subjects receiving high and low
MMT dose, with and without
chronic pain, and in 17 healthy controls. The characteristics of
chronic pain were also evaluated.
MMT dose and
chronic pain differentially affected pain perception. Whereas
MMT dose did not affect thresholds,
chronic pain MMT subjects exhibited increased pain threshold and
pain-free MMT subjects exhibited decreased pain threshold compared with controls.
MMT in general was associated with decreased perception of suprathreshold
pain; however,
MMT subjects with
chronic pain exhibited increased suprathreshold
pain ratings. It appears that subjects receiving
MMT are hyperalgesic but that
chronic pain in these subjects interferes with threshold measurements, inducing an apparent hypoalgesia. On the other hand,
chronic pain reduces the
analgesic effect of
methadone seen in
pain-free MMT subjects, amplifying suprathreshold pain perception. Factors such as
chronic pain and
MMT dose should be taken into account in future studies on pain perception in this population.
PERSPECTIVE: We show that the presence of
chronic pain and
methadone dose significantly affects perception of
pain in former
heroin addicts receiving
MMT. Studying the alteration in pain perception in these subjects may contribute to understanding the high rates of
chronic pain among them and may promote better treatment.