The popular painkiller Paracetamol is New Zealand's most widely taken medicine with almost 2.5 million prescriptions every year. That's almost double the number issued for the country's number 2 medicine, aspirin.
Those figures don't include the stuff we buy over the counter, or all the combination treatments it's sold in either. But we still don't really understand how paracetamol works.
John Ashton is a Senior Lecturer in the Department of Pharmacology & Toxicology at the Otago School of Medical Sciences.