There's concerns tramadol could be getting over-prescribed, with more patients being given the painkiller.
Pharmac data shows more than 270,000 people were prescribed the drug last year - an increase of 14 percent since 2019.
UOA School of Pharmacy lecturer Dr Jay Gong says healthcare providers likely prefer prescribing tramadol over stronger painkillers.
"There might be some perceived ideas around it - because it's a weaker opioid, it's maybe not as addictive and maybe in the long run, you might not have as much side effects."
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