Tamworth Hospital, in the state's north, accounted for the most incidents, where there were 30 notifications of unaccounted Schedule 8 and Schedule 4 drugs.

Under NSW's access to information laws, ACM has found that every month over a two-year period, drugs including oxycodone, morphine, methadone and fentanyl were reported as lost, missing or stolen from the region's hospitals and health facilities.

Despite these medications being closely monitored "under lock and key", there were almost 140 occasions where prescription-only and controlled drugs went missing from Hunter New England Health (HNEH) facilities between March 2018 and June 2020.

At John Hunter Hospital during the same period, medications such as fentanyl and oxycodone were reported as missing or stolen on 19 occasions.

There were 16 notifications at Manning Base, 13 at Muswellbrook, and 10 at Maitland Hospital in the state's Hunter Valley.

The drug accounting for the most notifications was oxycodone, with 34 references to the opioid being lost or stolen in that two year period.

The street value of the highly addictive and easily abused opioid - according to reports online - is about $40 a tablet.

But fentanyl - which has a street value range between $74 to $450 a patch and $99 per gram on average - accounted for 26 notifications.

Fentanyl is 50 times stronger than heroin, with fentanyl patches posing the "biggest risk" due to the unpredictability of the "street extraction process," Hunter GP Dr David Outridge said.

The region's health services have processes in place to destroy the slow-release opioid patches immediately after they are removed from patients to prevent people from fossicking through the bins and finding any remnants of the potent and potentially deadly drug.

There were 28 incidences of midazolam - a benzodiazepine medication used for anesthesia, sedation, insomnia, and severe agitation - reported missing.

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And 16 cases of methadone reported as lost or stolen.

The report said that while it was known that prescription medicines were subject to abuse and trafficking in the community, there had been no suggestion from police that the missing medications were a source of street trafficking.

Cases involving large quantities of accountable medicines, where diversion may be suspected, or where a specific suspect cannot be identified, are referred to police for investigation.

Dr Outridge, who works in addiction medicine, said the allure of these types of drugs was the "euphoria" they could create, and the pain relief.

"There are two main groups," he said.

"There are the people that come across opiates through a medical reason.

"They may have broken a leg and are exposed to it and they find this drug also helps their emotional state or emotional pain. The other group may tend to use more recreational drugs and self-medicate.

"They tend to progress through the recreational and self-treating phase into addiction with repeated use.

"It's also not uncommon to find people who have started heroin use at 12 or 13.

"They may come from a difficult background, and there is a lot of substance abuse in their peer group.

"Then when they find an opiate like oxycodone, as they use it more, they become dependent. There is the withdrawal to get through, as well as the pleasure of using."

Dr Outridge said fentanyl was a potent, synthetic opiate which had become a major issue in the US, and "alfentanil" was 10 times more powerful again.

There was one logged incident of alfentanil being reported as missing or stolen from Tamworth Hospital in August 2019.

Dr Outridge said people often boiled up fentanyl patches to extract the drug.

But this "bucket chemistry" process was "extremely dangerous".

"They may not know what they are doing, but they also don't know how much of the drug they are managing to get out of the patch," Dr Outridge said.

"It may be the difference between life and death.

"Fentanyl has a more rapid onset than heroin.

"With heroin - it might take a few minutes for the overdose to come on. They might start getting sleepy and breathing more slowly and gradually stop breathing.

"With fentanyl, it's a much more rapid onset. Therefore it is more deadly."

Dr Outridge said while the drugs were closely watched, there were some settings in hospitals - which required quicker, easier access to certain drugs - where monitoring the medications was less controllable, and relied on the integrity of the staff.

He has previously supported Hunter health staff with access to pharmaceutical drugs.

"Addiction doesn't discriminate," he said.

But while "he hadn't seen much" evidence of fentanyl abuse in the Newcastle community, oxycodone remained the most popular pharmaceutical drug on the street.

The information provided by NSW Health under the GIPA Act does not specify what quantities of the medications were reported as missing.

But a spokesperson said there had been no notifications received from police "or any other source" that reported losses at hospitals were a source of street trafficking.

"People authorised to possess Schedule 8 and Schedule 4 drugs are required by law to report if they are lost or stolen to the Ministry of Health," the spokesperson said.

"This requirement includes pharmacists, doctors, dentists, veterinary practitioners, residential care facilities and licensed wholesale distributors - not just public and private hospitals.

"In the broader context of the large volumes of medicines used in public hospitals, the number of lost or stolen medicines is very small.

"Most reports received by the Ministry of Health involve very small quantities, many attributed to a single tablet or glass ampoule being dropped or spilled, rendering them unusable."

The spokesperson said all Schedule 8 and Schedule 4 medicines were required to be stored "under lock and key" with restricted access, and every movement - including the receipt at ward level and administration to a patient - separately recorded.

"In NSW public hospitals, these drug register entries are required to be checked at least once every 24 hours. Incidents of unaccountable losses are investigated at hospital level," they said.

"Where patterns of concern are identified, an overall review may be conducted by the local health district or by the Ministry's Pharmaceutical Regulatory Unit."

When ACM applied for this information, first through HNEH, the health district said it had no central record of stolen, missing, or lost medications from its hospitals or health facilities. This was despite the district supplying this information twice before - once to ACM in 2009, and again to ABC Newcastle in 2015.

An internal review and lost appeal established the information was held with the Ministry of Health's Pharmaceutical Regulatory Unit.

An application to this unit for the information in July, 2020, took a year to be processed and released back to ACM.

In its final decision, the Ministry of Health wrote: "For future GIPA requests for this type of information/data, we ask that you apply directly to HNEH.

"HNEH has recently been confirmed that they now have the capability to run these reports and are now able to respond to these types of requests directly."

Hunter New England Health chief executive Michael DiRienzo said the district took the loss of any drugs "very seriously and any reports of missing pharmaceuticals are investigated thoroughly".

He said notifiable accountable medication incidents included all incidents of loss, including through damage.

"Incidents involving unaccountable loss - where medication is diverted or stolen - are extremely rare," he said.

He said the district had strict protocols in place to report and investigate when drugs go missing.

All incidents of missing drugs must be reported to the director of nursing as well as the director of pharmacy.

Any lost or stolen Schedule 4 or 8 drugs are reported to the NSW Ministry of Health.

"We are continuing to look at ways to strengthen medication security throughout the District. Recent enhancements to drug security include reinforced procedures around medication security and regular audits to ensure medications are being kept safely," Mr DiRienzo said.