Discovered in 1832 by Pierre Jean Robiquet, codeine (aka 3-methylmorphine) appears on the World Health Organisation's List of Essential Medicines.
In New Zealand, small amounts of codeine can be bought over the counter without a prescription – in drugs like Panadeine, Nurofen Plus and Codral.
But with the use of opioid painkillers like morphine and codeine quadrupling over the last decade and worries about codeine addiction and abuse, there are now calls to make medicines containing codeine prescription-only.
John Ashton is a Senior Lecturer in the Department of Pharmacology & Toxicology at the Otago School of Medical Sciences.
