Toxicology Laboratories, VA North Texas Health Care System, Dallas, TX 75216, USA
Roche Diagnostics/Boehringer Mannheim Corporation, Pleasanton, CA 94566, USA

Consecutive patient urine samples (480) submitted for methadone screening were obtained from 106 male subjects (mean age of 48.6 years- range 31-69). The average length of opiate use was 255 months (range 8-516). The average length of methadone treatment was a 165 weeks (range 1-1 361) and the mean daily dosage of methadone was 43 mg per day (range 20-90).

Of the 480 samples, 397 were positive for methadone and EDDP, 45 were positive for EDDP but negative for methadone while 19 specimens were positive for methadone but negative for EDDP. Nineteen urine samples were also negative for both methadone and EDDP. Of most interest in this study were the 45 samples with EDDP levels greater than 1 00 ng/mL but which were negative for methadone. These specimens, representing 9.4% of the samples, are most likely from patients who exhibit either genetically determined or drug induced rapid metabolism of methadone and for whom a methadone screen used alone, would return a false negative and an incorrect clinical conclusion. Longitudinal data on the ability to detect methadone use using both methadone and EDDP assays will be presented.