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 require however 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. Forty-three participants, all on methadone and heroin-assisted treatment, were studied. Participants were monitored after the first and right before the second dosage of heroin. At both time points oral fluid and exhaled breath samples were collected with urine at the second time point. All samples were screened for opiates, methadone and other drugs using immunoassay and LC-MSMS. At the second time point, 98 percent of oral fluid samples and all exhaled breath samples tested positive for 6-monoacetylmorphine (6-MAM). Regarding morphine detection, the findings were reversed (100 percent in oral fluid, 98 percent in exhaled breath). Methadone-related results were 100 percent positive across all matrices, as expected. Notable is the detection of the heroin marker acetylcodeine in oral fluid and exhaled breath samples, which resulted in relatively low negative predictive value (average 54.6 percent). Oral fluid and exhaled breath are suitable alternatives for heroin and methadone maintenance monitoring. Clinicians should consider ease of collection, adulteration risk, costs, turn-around time, and the substance of interest while choosing a matrix. In addition, even in cases when medicinal heroin is used, medical professionals should be aware of the presence of acetylcodeine in these alternate matrices.