SOFT - TIAFT 1998 Poster Session 2 Wednesday October 7, 1998

F. Roark Galloway, Craig Lingenfelter and Neal F. Bellet

Roche Diagnostics/Boehringer Mannheim Corporation, Pleasanton, CA, USA

During validation of a GC/MS method for the methadone metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), it was noted that detectable levels of EDDP were found during analysis of drug-free urine samples spiked with methadone. To verify this observation, extracts of methadone-spiked urine samples were analyzed by GC/MS and reverse-phase HPLC. While the HPLC method indicated no EDDP in the extracts, GC/MS data clearly identified EDDP by retention time and selected ion mass (SIM) fragmentation data. Quantitative analysis of methadone conversion to EDDP by GC/MS was performed using EDDP-D3 as internal standard and measuring the resulting GC/MS-SIM signal data. The amount of EDDP observed was variable, but was consistently > 50 ng/mL at methadone concentrations > 10,000 ng/mL. In one case, reducing the GC injector port temperature from 260° C to 180° C reduced the observed EDDP concentration from 201 ng/mL to 53 ng/mL at an initial methadone sample concentration of 10,000 ng/mL.

These findings were valuable in verifying the accuracy of a recently-developed immunoassay specific for EDDP [CEDIA® DAU EDDP (Methadone Metabolite) Assay, Boehringer Mannheim Corp.]. Urine samples spiked with high concentrations of methadone were negative by the immunoassay method, but positive by GC/MS. The HPLC method was used to confirm the absence of EDDP in spiked samples, as well as in a small percentage of samples from methadone treatment clinics which, by the CEDIA® immunoassay method, tested strongly positive for methadone but negative for EDDP. These samples were suspected to result from surreptitious addition of methadone to urine samples by patients who divert and sell the majority of their methadone dosage. In conclusion, alternative methods (i.e., HPLC or LC/MS) should be considered when determining the concentration of EDDP in samples containing high concentrations of methadone.

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