New Zealand's high poison deaths a concern, expert says

The study represented the largest published review of New Zealand coronial data to examine poison-related deaths. Photo / File

Experts are calling for tighter restrictions on some mental health drugs following new figures that reveal an alarming number of people have died after taking them.

The New Zealand-first study, carried out by the University of Otago and the Best Practice Advocacy Centre, has revealed 1402 deaths related to poison between 2008 and 2013.

Lead author of the study Dr John Fountain said throughout the six-year review period there were unexpectedly high numbers of deaths due to the hypno-sedative drug zopiclone, used to treat insomnia, and the antipsychotic drug, clozapine.

While zopiclone is classified as a controlled drug in a number of countries, this restriction does not apply in New Zealand, only a recommendation that it not be prescribed for more than four weeks, Fountain said.

He said clozapine was responsible for the majority of anti-psychotic-related deaths in the study.

"This is despite its prescription being largely restricted to psychiatrists or those under their supervision and a formal patient monitoring system," Fountain said.

He stressed these findings indicated the causes of death due to poisoning were changing over time in New Zealand and interventions were needed to reduce death rates.

Fountain suggested the removal of subsidies for medicines with low efficacy and high toxicity, or increasing prescriber's awareness of the toxicity of certain pharmaceuticals.

Pharmaceuticals accounted for 52 per cent of the 1402 deaths, with methadone taking the lead and the third most common drug overall.

Morphine and codeine followed, with zopiclone and clozapine equally ranked as the sixth most common cause.

Fountain said that methadone was a drug that was heavily abused with many people tending to accidentally overdose on it.

The data also revealed poisoning was higher in males, 6.9 per 100,000 people, than females, 3.83 per 100,000.

The study represented the largest published review of New Zealand coronial data to examine poison-related deaths.