A child took SIX DOSES of a heroin substitute intended for an addict after a Boots pharmacist gave her mother the wrong medicine.
The girl should have been prescribed an antibiotic but the pharmacist presumed her mum was the addict and handed over methadone instead.
Details of the mistake were revealed in information released by the NHS under Freedom of Information laws, the Daily Mail reports.
The mix-up took place when the child's mother went into the 24 hour branch of Boots to collect a repeat prescription of Flucloxacillin, an antibiotic commonly used to treat children's chest infections.
But staff at the chemist's appeared to mistake the mother for an addict who regularly picked up her methadone prescription from the same branch.
Instead of giving the mother the antibiotic, staff at the branch handed over the powerful heroin substitute, which has strict guidelines about how it should be dispensed.
Later the same day, the addict arrived at the Boots branch to collect her methadone but a different pharmacist refused to hand it over, saying their records showed it had already been given out.
The report says that the mother then gave her daughter 5ml doses of methadone believing the medicine was the antibiotic her daughter had previously been prescribed.
By the time the blunder was uncovered the child had taken 30g of methadone in a total of six 5ml doses.
She was taken to hospital where medical staff cared for her while the effects of the drug wore off.
A spokesman for the company said: "At Boots UK everything we do, every day, is about how we care for our customers and patient safety is at the heart of our business.
"Our pharmacists adhere to the strict guidelines around issuing methadone.
"We conducted a full and thorough review of our practices at the time of this incident in 2011."