Pupillometry in the detection of concomitant drug use in opioid-maintained patients

Pupillometry and ocular response measures are sensitive to a variety of acutely administered drugs and as such are useful for drug detection and fitness-for-duty applications. The utility of pupillometry to complement urine testing in methadone clinics, where there is considerable non-therapeutic drug use, has not been tested. A video-based pupillometer (FIT 2000) was evaluated in 37 opioid-maintained patients. Three times a week they provided urine samples and pupillometry measures of: initial diameter (ID) in mm; constriction amplitude (CA) in mm; constriction latency (CL) in msec; and saccadic velocity (SV) in mm/sec. Analysis of the success rates indicated that 92.9% of subjects obtained an acceptable reading, 59% on the first attempt. Low variability in pupillary parameters on drug-free days are necessary for effective identification of concomitant drug use. The variability (standard deviation) of ID (0.51 vs. 0.68), CA (0.12 vs. 0.27) and SV (7.2 vs. 11.1) increased on days when the urine was positive for abused drugs compared with drug-free urine days in subjects (n = 6). Subjects who were always drug-free (n = 4) had lower variability than those who always had urine positive for additional drugs (n = 20). These preliminary results suggest that pupillometry may be useful to verify concomitant drug use in a methadone-maintained population. Successful implementation of the methodology could reduce costly and intrusive urine testing.