The role of methadone in the death in custody of Steven Freeman in Canberra's jail last May is being examined in a coronial inquest, as he died just two days after being put on the opioid program.

While such treatment for recovering opioid-dependent people is common and accepted, it comes with serious risks for those who are not opiod-dependent, a central question the inquest is investigating.

The Canberra Times can report a review of the guidelines governing opioid maintenance treatment across the prison system and the wider community, meant to be completed by September 2012, has still not been completed almost five years later.

An ACT Health spokesman said the review began in June 2012, but was delayed for two years to reflect "best practice" in new national guidelines completed in 2014.

But the directorate has refused to explain why, more than three years after the 2014 national guidelines were released, the ACT's guidelines have still not been updated.

He said reviews of such clinical guidelines were "ongoing" across the health system, and it was "important to note that it is not unusual for clinical guidelines to remain relatively static for significant periods of time".

"Once a guideline is in place, it is unusual for the guideline to be updated unless there are material changes in the evidence base derived from the medical and scientific literature," he said.

While the existing guidelines are still being followed in opioid prescribing in the community, the lengthy delays mean those guidelines have not been updated since they were approved by the legislative assembly in January 2010.

The health spokesman said that the review would be "finalised later this year" and that the opioid treatment clinical advisory committee (OTCAC), an advisory group that oversees the rules, had "played a constant monitoring role" in the years since.

But The Canberra Times understands the committee agreed on a draft version of the guidelines last year, but that draft is yet to be approved by the health directorate or receive ministerial approval and the committee had not met since November last year.

Questions put to the health directorate about the frequency of the committee's meetings remain unanswered.

The justice health service has made a series of changes to the AMC's methadone program since Freeman's death, including reducing the initial starting dose for inmates from 30mg to 20mg, and new rules around monitoring the 120 inmates currently prescribed methadone.

While the health spokesman said both 20mg and 30mg were compliant with the current national guidelines, those rules also recommend starting patients on 20mg or less if they have "low or uncertain" opioid dependence, use multiple drugs or alcohol or have other severe medical complications.

The guidelines also show the 30mg dose that was previously the usual starting dose at the AMC was the upper limit recommended and "higher doses" between 30mg and 40mg should be considered "with caution, if clinically indicated, at the discretion of the prescriber".

The health directorate is also working on a new electronic methadone dosing system for inmates, to replace the existing manual system, expected to be completed in August this year.