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Methadone

Interpretation

  • The clearance half-life of methadone averages 30 hours. Urinary methadone excretion is pH dependent; excretion is decreased with increased urinary pH.
  • Patients who are taking methadone for therapeutic purposes excrete both parent methadone and metabolite in their urine.
  • The absolute concentration found in a patient’s urine sample can be highly variable; however, patients who are known to be compliant with their methadone therapy have ratios of EDDP:methadone >0.60.
  • If there is a question as to a patient's therapeutic compliance, a serum test request for the specific drug of interest may be of help.
  • The presence of methadone >LOQ indicates exposure to methadone within 6 to 7 days prior to specimen collection.

Metabolites

  • Methadone is metabolized to an inactive metabolite, 2-ethylidene-1,5-dimethyl-3,3- diphenylpyrrolidine (EDDP).

    Methadone 2-Ethylidene-1,5-dimethyl-3,3- diphenylpyrrolidine (EDDP)

Approximate Detection Times

Methadone LOQ (ng/mL) Detection Time* up to
     Methadone
100
7 days
     EDDP (methadone metabolite)
100
7 days
*These are approximate detection times for the drug or metabolites in urine. The actual detection time depends on dose, frequency of use, and individual metabolism.


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