Is opioid-induced hyperalgesia reversible? A study on active and former opioid addicts and drug naïve controls.

OBJECTIVE

Hyperalgesia has been observed in active opioid addicts (OAs). The aim of this study was to explore whether opioid-induced hyperalgesia (OIH) is a reversible phenomenon.

DESIGN

Observational study.

PARTICIPANTS

The study included the following three groups of male subjects: 1) active addicts on heroin or methadone (OAs, n = 50); 2) former opioid addicts with at least 5 months of abstinence from drug use (FOAs, n = 43); and 3) drug naïve controls (C, n = 50).

INTERVENTIONS: All subjects were exposed to the cold pressor test (1°C).

MAIN OUTCOME MEASURES: Cold pain threshold (latency to pain onset, seconds) and cold pain tolerance (latency to pain intolerability, seconds).

RESULTS

Mean ± standard deviation (SD) pain thresholds were 10.8 ± 7.7, 6.9 ± 3.9, and 6.8 ± 3.5 seconds for the OAs, FOAs, and C groups, respectively (analysis of variance [ANOVA], p = 0.002, 95% CI = 7.5-9.2). Mean ± SD pain tolerance levels were 30 ± 36.2, 64 ± 58.1, and 56.4 ± 51.4 seconds for the OAs, FOAs, and C groups, respectively (ANOVA, p < 0.001, 95% CI = 43-60.4). Post hoc analyses revealed significant changes between the OAs and the other two groups for both variables.

CONCLUSIONS

It is suggested that altered pain perception in OAs is a reversible phenomenon that may require a long period of abstinence to reset, rather than being an individual long-term stable trait.