The Guidelines are based on the principles that people who use drugs have the same entitlement as other patients to the services provided by the HSE. Service users have a right to be heard, listened to and taken seriously and should be consulted and involved in all matters and decisions that may affect their lives. The Guidelines have been developed in order to outline evidence-based care to standardise and improve the quality and safety of care to the patient.

The main illicit opioid used in Europe is heroin, which may be smoked, snorted, or injected. A range of other synthetic opioids are also illicitly available, such as Oxynorm/Oxycontin, codeine, fentanyl, methadone, and buprenorphine. In 2011, eleven European countries reported that 10% or more of their first-time opioid clients entering specialised treatment were using opioids other than heroin.

In Ireland, Opioid Substitution Treatment (OST) refers to the provision of both methadone and buprenorphine/ buprenorphine-naloxone. At the end of 2014, there were 9764 people in receipt of OST in HSE Addiction Clinics and GPs, compared with 9,116 in 2013. There were 726 new first time patients in 2014, compared to 552 first time patients in 2013. There were 468 people in receipt of OST in prisons, compared to 539 in December 2013. There were 159 new first