Towards adherence monitoring using breath or oral fluid as a matrix in a methadone maintenance treatment program for patients with a chronic heroin use disorder: Issues and interpretation of the results.

Urine has been the preferred matrix for monitoring heroin and methadone adherence due to its large detection window. Drawbacks such as privacy concerns and adulteration however require other matrices. The study aims to determine if oral fluid and exhaled breath are suitable alternatives for heroin and methadone monitoring and to assess the detection time in exhaled breath.