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.

Roadside detection of impairment under the influence of ketamine--evaluation of ketamine impairment symptoms with reference to its concentration in oral fluid and urine.

Although there are many roadside testing devices available for the screening of abused drugs, none of them can be used for the detection of ketamine, a popular abused drug in Hong Kong. In connection to local drug driving legislation, effective roadside detection of ketamine in suspected drug-impaired drivers has to be established. According to the drug evaluation and classification program (DEC), ketamine is classified in the phencyclidine (PCP) category. However, no study has been performed regarding the signs and symptoms exhibited by users under the influence of ketamine. In a study to develop a protocol for effective roadside detection of drug-impaired drivers, 62 volunteers exiting from discos were assessed using field impairment tests (FIT) that included measurements of three vital signs (i.e. body temperature, pulse rate and blood pressure), three eye examinations [pupil size, lack of convergence (LOC) and horizontal gaze nystagmus (HGN)] and four divided attention tests (Romberg, one-leg stand, finger-to-nose and walk-and-turn tests). Subsequent laboratory analysis of oral fluid and urine samples from the participants revealed the presence of common abused drugs in both the urine and oral fluid samples of 55 subjects. The remaining 7 subjects with no drug in their oral fluid samples were used as drug-free subjects. In addition, 10 volunteers from the laboratory who were regarded as drug-free subjects were also assessed using the same FIT. Among the 62 volunteers, 39 of them were detected with ketamine in their oral fluid. Of these ketamine users, 21 of them (54%) with only ketamine found in their oral fluid samples while the rest (18 subjects) of them had other drugs (i.e. MA, MDMA, benzodiazepines and/or THC) in addition to ketamine. Of the 21 ketamine-only users, 15 of them (71%) were successfully identified by FIT. It was found that when salivary ketamine concentrations were greater than 300 ng/mL, signs of impairment became evident, with over 90% detection rate using the FIT. By comparing the FIT observations on the 21 ketamine-only users with the drug-free subjects, the typical signs and symptoms observable for subjects under the influence of ketamine included LOC, HGN, elevated pulse rate and in general, failing the divided attention tests, especially the walk-and-turn and one-leg stand.