Pain response in heroin users: personality, abstinence, and modulation by benzodiazepines.

We compared cold-pain responses among male current opioid users with and without concurrent benzodiazepine use, long-term ex-users, and healthy controls. Forty-eight current opioid users (14 concurrently using benzodiazepines), 34 ex-users (abstinent for ≥1 y) and 63 controls received cold-pressor tests. Pain threshold (first reporting pain) and pain tolerance (total immersion time) were recorded. Pain thresholds were similar in ex-users and current users; pain tolerance was similar in ex-users and controls. Net pain tolerance (endurance) in ex-users was intermediate between the other two groups. Current users showed higher pain threshold and shorter pain tolerance than controls (p<0.05). Current users not co-using benzodiazepines showed the lowest pain tolerance and net pain tolerance, and differed significantly from controls, ex-users, and current users co-using benzodiazepines (p<0.05). Neuroticism was higher in current users than in the other two groups (p<0.001), extraversion marginally lower (p<0.05); net pain tolerance differences remained significant after controlling for these. Benzodiazepine use modulates pain tolerance in opioid users. Pain responses altered by opioid use may partially recover with abstinence.