Substance Use and Heroin Abstinence Rates Among Patients Enrolled at a Medically-assisted Therapy Clinic in Kenya: a Retrospective Cohort Study

Background: Methadone Maintenance Treatment (MMT) has been shown to be beneficial in several evidence-based studies. However, patients who were using multiple substances at the time of enrollment impacted the program's outcomes. Studies have shown that even while enrolled in the program, patients continue to use heroin and other drugs. The purpose of this study was to determine the rates of substance use and heroin abstinence among patients attending the Medically-Assisted Therapy Clinic in Nairobi, Kenya. Methods: We conducted a retrospective cohort study on 713 patients who had enrolled in the Medically Assisted Therapy (MAT) clinic between December 2014 and February 2018. Each participant's data was collected over a 24-month period. A researcher-designed socio-demographic form and data collecting form were used to collect data. Data were analysed using SPSS version 26.0. Results: Most participants were males 611(85.7%). The mean age was 34.2 years (SD 8.55). The majority had attained primary level of education 333(46.7%), were employed 424(59.47%), and were separated 322(45.1%). All the participants had used at least one other substance apart from heroin. The commonest substances were; tobacco 649(91%), followed by cannabis 591(82.9%) and benzodiazepines 367(51.5%). At 6, 12, 18, and 24 months, heroin abstinence rates were 61.3%, 76.0%, 73.5%, and 81.4%, respectively. Abstinence rates increased from 61.3% at 6 months to 81.4% at 24 months, which was statistically significant (p < 0.001). Conclusions: The majority of the patients attending MAT clinic use more than one substance. There is a need to scale up the program to also offer free management for other substances. This study replicated the evidence of methadone treatment among heroin users. However, there is still a need to explore further why some patients continue to use heroin while in the program.