One reason for the excitement about Exanta is that one dosage level seems to work equally well for most people.

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Mr Beed claimed Dr Barton set the parameters for the dosage but the level used was applied on the agreement of two nurses.

BBC: Gladys Richards

An addictions specialist told the inquiry the dosage was "too high" given the uncertainty about Mr Nichol's tolerance level.

BBC: Borders clinic methadone death 'avoidable'