A TGA review has found little evidence to support the efficacy and safety of over-the-counter-codeine.

The independent review of the literature carried out by researchers from the George Institute was commissioned to help the government make an impending decision on whether OTC should be rescheduled.

It found there was evidence to suggest that combination codeine medicines – with paracetamol or NSAID and or caffeine — provided significantly greater pain relief compared with placebo.

“In single dose trials combination medicines provided clinically significant pain relief for the immediate term however these effects appear to decline in the short term (between 4-6 hours after a single dose)” the review stated.

However none of the studies reported on efficacy outcomes beyond 12 hours making it difficult to extrapolate efficacy outcomes beyond the ‘intermediate’ term.

The review authors said it was also surprising that there were no eligible placebo controlled trials evaluating codeine combination medicines for headache or back pain “despite evidence to suggest these conditions are among the most common reasons for use and misuse of combination codeine medicines”.

The review also found limited data on adverse events outcomes, however nausea, tiredness, dizziness and GI upset were higher in treatment groups compared to placebo.

“Evidence on long term outcomes is lacking and it is not possible to determine prevalence of abuse/dependency based on the RCTS included,” it said.

The review analysed data from 14 placebo-controlled randomised controlled trials.