A new study looking at the health impacts of over-the-counter painkillers has revealed the high cost of Australia's growing dependency on codeine.

People struggling with chronic back pain and headaches are consuming up to five times the recommended daily dose of over-the-counter codeine painkillers at a huge cost to them and the health system, a new study has found.

A review of hospital admissions at a single hospital in Adelaide's south found misuse of over-the-counter combination painkillers containing codeine (OTC-CACC) cost the Australian health system more than a million dollars over five years.

Lead investigator Dr Jacinta Johnson of the study - published in journal Drug and Alcohol Review - says the "serious misuse" of codeine-combination products such as Nurofen Plus, Panadeine Extra and Mersyndol had led to increasing numbers of people being admitted to hospital with stomach ulcers and gastric bleeding, and acute kidney and liver failure.

The pharmacist at University of South Australia says restricting the sale of codeine containing medications is only part of the issue and there's a need to intervene earlier to help those suffering from chronic pain and misuse issues.

"We have been spending a lot on these patients anyway, so perhaps we should spend the money sooner and invest in more comprehensive pain management programs and options for patients out in communities before they get to the point that they are reliant on painkillers to manage their pain," Dr Johnson told AAP.

Researchers conducted the study after a decision by the federal government's health regulatory body to ban OTC access to codeine containing products from Australian pharmacies from February 2018.

The five year retrospective review of hospital records identified 99 codeine-related admissions for 30 individual patients from 2010-2015.

Almost 70 per cent were admitted with health issues relating to taking excessive amounts of ibuprofen-codeine products, while 20 per cent reported using paracetamol-codeine products and almost 9.4 per cent used both.

On average, the patients had consumed 28 tablets a day for more than 600 days prior to admission, mainly to treat back pain, migraine and headaches.

Alarmingly, some patients were using this amount for up to 10 years, Dr Johnson said.

On average, the patients stayed for six days and cost more than $10,000 each, with one in ten admitted to intensive care.

"This study is the first, to our knowledge, to quantify the costs associated with hospital admissions due to OTC-CACC misuse," the authors wrote.

Currently, a person has to speak to a pharmacist directly to purchase codeine products. However after February these products will only be available on prescription.

But access is only part of the solution to addressing dependency, Dr Johnson said.

"We do still see plenty of hospitalisations for patients using prescription painkillers and there is a risk that they may go onto stronger painkillers and end up with further complications there.

"So I think it is really important that GPs are ready to help manage these patients who do have to change from over-the-counter options and that we don't just jump to prescribing for them and look at their pain in a more comprehensive way," she said.