Keywords: recommendations or guidelines; health care professionals; physician; social worker; pharmacist; AOD use, abuse, and dependence; AOD dependent; AOD user; risk assessment; AOD effects and AODR problems; AODR mortality; harm reduction; communicable disease; HIV infection; viral hepatitis; diagnosis; health; mental health; psychological development; hair analysis; urinalysis; hematologic test; treatment and maintenance; drug therapy; intravenous injection; opioids in any form; methadone maintenance; buprenorphine; codeine; naltrexone; clonidine; treatment goals; relapse prevention; international area; United Kingdom; drug substitution therapy