Pupillary response to methadone challenge in heroin users.

The relationship between self-reported illicit heroin use and pupillary response to a low-dose methadone challenge was examined in 28 men beginning methadone therapy for opiate dependence. Pupil diameter was assessed before and 60, 90, and 120 minutes after a 20 mg methadone dose on day 1 of treatment. Self-reports of opiate drug effects were also taken at these times. There was a significant negative correlation (r = -0.53) between pupillary constriction 120 minutes after drug dosing and the average dollar value of subjects' reported heroin use per week. In other words, those who showed the least pupillary constriction generally reported the highest amount of illicit heroin use. Total years since first opiate use was also a significant predictor of pupillary response (r = -0.46). Self-reported amount of heroin use and years since first opiate use together accounted for 60% of the total variance in pupillary response to the challenge (Mult r = 0.77). Pupillary response to a low-dose methadone challenge appears to be a clinically practical and objective method for determining opiate tolerance levels in applicants for methadone therapy.