A validated liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometric method for the quantification of methadone, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), and 2-Ethyl-5-methyl-3,3-diphenylpyroline (EMDP) in human breast milk.

This manuscript details a validated liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry (LC-APCI-MS-MS) method for the quantification of methadone and its metabolites 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) and 2-ethyl-5-methyl-3,3-diphenylpyroline (EMDP) in 0.5 mL human breast milk. Limits of detection were 5 ng/mL for methadone and EDDP, and 10 ng/mL for EMDP. Linearity ranged from 10 to 500 ng/mL for all analytes. Breast milk is a complex biological fluid, necessitating several specimen preparation steps to separate methadone and metabolites from the lipophilic matrix. Recoveries were 66-97% following protein precipitation and solid-phase extraction with minimal matrix effect. Acceptable accuracy (89-101%) and precision (15-20% RSD) were achieved for all analytes. This is the first LC-APCI-MS-MS method for the sensitive and specific detection of methadone, EDDP, and EMDP in human breast milk. The method proved suitable for quantification of methadone and metabolites in breast milk of methadone-maintained opiate-dependent women.