A woman developed mental health problems and later died after taking part in trials of a cannabis-based drug, an inquest has heard.
Sativex is made from the cannabis plant
Diabetic Rene Anderson, aged 69 from Sheffield, was taken to hospital after starting to take Sativex to see if it would relieve pain she was suffering.
She died in March 2004 from acute kidney failure.
The continuing inquest is expected to have implications for the use of drugs derived from cannabis.
Mrs Anderson, a retired supermarket supervisor from Silkstone Close in Frecheville, had been taking part in a trial supervised by diabetes expert Dr Solomon Tesfaye.
He told the court he wanted to investigate whether cannabis could provide useful relief from the severe pain experienced by diabetic neuropathy sufferers.
Sativex, which is not yet licensed in the UK but has been granted a licence in Canada, had shown good results in multiple sclerosis sufferers, Dr Resfaye said.
He was first aware of Mrs Anderson's case when her family complained about her mental problems just days after her treatment began.
Admitted to hospital
The doctor said the dose of the drug, which is taken using an oral spray, was reduced but Mrs Anderson's daughter, Jackie Sadler, rang back two weeks later to tell of her mother's deterioration.
Sheffield coroner Chris Dorries heard how Mrs Anderson suffered a series of physical problems after she was admitted to hospital in October 2003, 23 days after starting to take Sativex
These included pneumonia which culminated in her death five months later.
The coroner said the purpose of the inquest was to examine what links there were, if any, between the experimental treatment and the physical deterioration which led to Mrs Anderson's death.
The inquest, which began on Monday, is expected to last five or six days.