Dr Gilvarry said Mr Nichol's dose went outside recommended guidelines
A young drug addict was prescribed too much methadone at a Borders clinic where he later died, a consultant psychiatrist has told an inquiry.
Kieran Nichol, 20, of Hawick, was given three doses totalling 90mg in little more than 24 hours in December 2005.
He was later found dead in his bed at the Castle Craig clinic near Peebles.
Dr Eilish Gilvarry, an addictions expert, said the dosage was "too high" given the uncertainty about Mr Nichol's tolerance level. The inquiry continues.
The fatal accident inquiry, at Edinburgh Sheriff Court, has heard Mr Nichol told clinic staff he had developed a £60-a-day heroin habit in less than two months.
However, his mother, Jacqueline Nichol, told the hearing her son had only smoked heroin twice and was not addicted to the drug.
The inquiry was also told no urine sample was taken from Mr Nichol to check for heroin use before he was prescribed methadone and diazepam.
He was given three 30mg doses of methadone despite showing signs of being over-medicated.
Dr Gilvarry said the initial dose should have been much lower and no further prescriptions should have been written until Mr Nichol showed signs of withdrawal.
She said an appropriate first dose would have been around 5mg, although the guidelines permitted up to 40mg.
But adding a further 60mg the following day was outside the guidelines, she said.
"I consider the doses of methadone and diazepam together slightly concerning, particularly in view of the inconsistent history," said Dr Gilvarry.
"I think the doses were too high."
She said medical staff should have closely monitored Mr Nichol for symptoms of withdrawal after giving him the first dose.
She added that nurses should have realised Mr Nichol was "over-sedated" and called an ambulance or the doctor instead of sending him to bed.
"It doesn't require specialist knowledge to recognise if someone is grossly sedated, I would expect any professional to recognise that," she added.
Mr Nichol died at the private hospital in Blyth Bridge on 11 December 2005.
The inquiry, before Sheriff Gordon Liddle, continues.