A coroner has ruled the death of a Tauranga man was accidental due to a failure to metabolise one of the various drugs he was prescribed.

Coroner Gordon Matenga's released his findings after an inquest into the death of 47-year-old Mark William Manukau held in Tauranga on September 19 last year.

His report revealed that about 3am on October 26, 2015 Mr Manukau, who was a resident at community mental health facility Emerge Aotearoa in Devonport Rd was feeling unwell.

He was found lying on the floor of his bedroom by support staff.

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The support worker unsuccessfully tried to rouse Mr Manukau but made him comfortable with a pillow and blanket and continued to monitor him during their shift.

Three hours later Mr Manukau was again feeling unwell and an ambulance was called to assess him, but it was decided ambulance support was not required, the report said.

By the afternoon shift, Mr Manukau agreed to shower with support, and he was helped to the edge of his bed, but could not stand and fell to floor complaining of stomach pains.

At 6.15am the next day he was again found on the floor by a support worker and was assisted into a sitting position in his bed but his breathing was laboured.

Mr Manukau was taken to Tauranga Hospital's Emergency Department by ambulance, but while being treated went into sudden cardio respiratory arrest, and despite efforts to revive him he died.

Mr Matenga said the deceased had a long standing history of schizophrenia, morbid obesity, gastrointestinal bleed and high cholesterol, and was being treated with a number of medications, including clozapine.

A post-mortem toxicology analysis showed a level of clozapine considerably higher than expected for normal use associated with clozapine-related fatalities, the report said.

Pathologist Dr Ian Beer concluded the death was due to clozapine toxicity.

Mr Matenga said he found Mr Manukau died as the result of "dilated cardiomyopathy in the setting of clozapine toxicity".

"I find his death was accidental. Mr Manukau took all medications that were prescribed to him by his doctor," he said.

Mr Matenga said he was satisfied there had been no opportunity for Mr Manukau to obtain clozapine from another source, nor secrete or stockpile clozapine. .

"I'm also satisfied that staff were careful with providing medication to Mr Manukau, and the correct procedures were followed," he said.

Mr Matenga said he accepted the elevated ante mortem blood concentration levels of clozapine in the months preceding Mr Manukau's death were an accumulation due to a failure to properly metabolise the drug.

He also acknowledged the probable potential effects of the concurrent use of the drugs Valproate, Chlorpromazine, Risperidone and Benztropine, which he was prescribed.