Table 4.

Summary of barriers and facilitators across key themes

Theme	Barriers	Facilitators
Public acceptance	− Public safety concerns (e.g., influx of PWUD, visibility of ‘scene’) − Concerns about crime, “Honey-Pot effect” − Increased demand for drug services − Stigma surrounding injection drug use − Promotion of permissive drug use attitudes	− Strict residency criteria for participants − Limited number of participants − Collaboration with local law enforcement − High-threshold treatment programs − Comprehensive drug policy frameworks (e.g., Switzerland) − Development of infrastructure and security measures
Legal and ethical considerations	− Legal barriers to prescription (prohibition of DAM for iOAT in most countries) − Stringent legal and regulatory requirements (dosage, formulation, administration) − Ethical concerns about patient consent and transitioning back to oral OAT − Tension between client needs and system requirements	− Changes in laws to allow DAM prescription − National ethics committees ensuring compliance with consent, autonomy, and protection protocols − Methodological standards imposed by ethics committees − Frameworks to reconcile patient autonomy with public acceptance concerns
Media coverage and interest groups	− Negative media campaigns (e.g., defamation, misinformation) − Public fears over “drug tourism” and stigma around heroin use − Moral outrage in public discourse − Resistance from abstinence advocates and political groups	− Comprehensive information strategies (e.g., publishing reports, organizing events) − Involvement of family members of people with an OUD and community in media strategies − Addressing opponents’ arguments proactively − Emphasizing moral responsibility and public health advocacy
Long-term implementation costs and benefits	− High start-up costs (staffing, recruitment, infrastructure) − Limited long-term economic justification for iOAT − Structural challenges (space, equipment) − Limited resources and political decisions affecting sustainability	− Demonstrated cost-effectiveness of iOAT (reduced crime, law enforcement costs) − Political support for long-term funding − Economic evaluations − Funding strategies, ringfenced funding, and capacity-building initiatives
Patients’ and providers’ perspectives	− Structural weaknesses in conventional treatment − Regulatory barriers (e.g., daily supervision, dose restrictions) − Reluctance among PWID to switch to iOAT − Concerns about infection risks and attachment to oral OAT rituals	− Patient-centered care (e.g., incorporating patient preferences in treatment decisions) − Flexibility in delivery protocols (e.g., take-home doses) − Peer support networks to engage harder-to-reach individuals − Inclusive spaces for women and gender-specific services − Interdisciplinary support

OAT opioid agonist treatment, iOAT injectable opioid agonist treatment, OUD opioid use disorder, PWUD people who use drugs, PWID people who inject drugs