The amount of codeine dispensed to Australians has halved since pharmacists were banned from selling the drug over the counter a year ago, the TGA says.

The regulator upscheduled the drug to prescription-only in February 2018, saying the risks of addiction and overdose or misuse were too high for codeine to be available without a doctor’s oversight.

A TGA-commissioned review of drug sales data showed that 8.25 tonnes of prescription codeine was dispensed by pharmacists in the 11 months after the ban started.

This compared with a projected amount without the ban of 15.2 tonnes, it said in a statement issued on Wednesday.