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Article History

Received: 8 September 2025

Accepted: 20 November 2025

First Online: 9 December 2025

Declarations

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: All procedures followed were in accordance with the ethical standards of the Responsible Committee on Human Experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2000. The study was reviewed and approved by the Senate Research and Publications Committee at the Muhimbili University of Health and Allied Sciences (DA.282/298/01.C/), the National Health Research Ethics Review Committee at the National Institute for Medical Research in Tanzania (NIMR/HQ/R.8a/Vol. IX/3334), and the Institutional Review Board at the Johns Hopkins University Bloomberg School of Public Health (IRB00009747). All participants provided oral informed consent prior to study participation, which was approved by the Senate Research and Publications Committee at the Muhimbili University of Health and Allied Sciences, the National Health Research Ethics Review Committee at the National Institute for Medical Research in Tanzania, and the Institutional Review Board at the Johns Hopkins University Bloomberg School of Public Health. Oral consent was obtained because the study was low risk and written consent would be the only record with the names of the people participating in the study and could have potentially placed participants at risk with local law enforcement, given the illegality of heroin use.

: N/A.

: The authors declare no competing interests.