METHADONE

Methadone is a long-acting synthetic opioid used both as a treatment for chronic pain and, more commonly, as an opioid-substitution therapy (OST) for opioid use disorder. Its half-life is 24–36 hours, much longer than morphine or heroin, which lets a single daily dose suppress withdrawal and cravings. The test measures methadone and often its main metabolite EDDP (2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine), which confirms actual metabolism rather than someone simply adding methadone to a urine sample.

Methadone is not routinely detected by standard opiate immunoassays — those target morphine-codeine-like opioids. A specific methadone assay is needed, and confirmation is by LC-MS/MS.

In India, methadone OST programmes run under the AIIMS National Drug Dependence Treatment Centre and ICMR-supported clinics, particularly in states with high heroin use (Punjab, Manipur, Mizoram). Confirming methadone presence and concentration matters in three settings: (1) verifying adherence in OST patients (a positive test = patient is taking the prescribed dose), (2) emergency assessment of opioid overdose (methadone overdose is dangerous because of its long half-life and QT-interval prolongation), and (3) pain-clinic monitoring of chronic-pain patients on prescribed methadone.

Methadone causes more drug-induced cardiac arrhythmias and overdose deaths than most opioids because of its narrow safety margin, slow metabolism, and major drug interactions (especially with QT-prolonging drugs and CYP3A4 inhibitors).

For OST adherence monitoring the sample is usually drawn at the clinic just before the next supervised dose (trough). For overdose evaluation, the sample is drawn on presentation — the timing relative to last dose is recorded. No fasting needed. Tell the lab and the clinic about all other medications, including herbal preparations, because many alter methadone metabolism.