Side Effects of Chronic Methadone Use in Opioid Addiction: A Scoping Review on Hematological Derangements

Background: Per oral methadone maintenance therapy [MMT] was introduced as part of harm reduction strategy to manage rising numbers of HIV infections caused by intravenous use of illicit drugs. Method: We aim to review published articles related to the side effects of long-term methadone therapy, focusing on hematological derangements in human studies published between 1 January 2000 till 31 January 2021. Results: Our search databases include Web of Science, Scopus, and Medline. Our search yielded 971 articles, of which 55 articles were related to the effects of MMT on various organ systems: cardiovascular [n=12], respiratory [n=1], endocrine [n=10], central nervous system [n=12], neurobehavioral [n=10], gastrointestinal [n=1], and bone [n=1]. There were eight articles specifically related to the hematological side effects of chronic methadone therapy that include [i] immune system hyperactivation, [ii] reduced circulating lymphocytes, and [iii] increased blood viscosity. Conclusion: In view of all foreseeable health risks seen with prolonged methadone therapy, pharmacological modulation is warranted to find a better substitute for managing patients with opioid dependence.