A woman in a vegetative state will be given a sleeping pill which may "wake her up" against her family's wishes.
Zolpidem works on nerve cells in the brain
The 53-year-old, who has not been named, will be given zolpidem which early research has shown can bring people out of a vegetative state.
Her family do not want the test to go ahead, preferring to let her die, as she may be left seriously disabled.
But Sir Mark Potter, head of the High Court's family division, ruled against their wishes earlier this month.
The drug proposal was put forward by Laurence Oates, the outgoing Official Solicitor, who suggested that zolpidem be prescribed, the Guardian newspaper reported.
It is normally used to help insomnia but has been cited in a number of cases where it has caused patients in a persistent vegetative state (PVS) to wake up.
An improvement was seen within 20 minutes of taking the drug and wore off after four hours, when the patients restored to their permanent vegetative state.
Professor Keith Andrews, who looks after severely brain-damaged patients at London's Royal Hospital for Neuro-disability, said the drug had not worked on the patients he had tried it on.
And he added: "I personally don't think it will work in this case."
But a spokesman for the Department for Constitutional Affairs said: "It is a very difficult situation.
"The Official Solicitor, who represents the woman, came to a view that was opposite to the family.
"He accepts that there are incredibly sensitive issues that need to be addressed with this family and the woman itself.
"But he also takes the view that there are other issues for other patients in this situation.
"He believes that no stone should be left unturned in trying to save life."
It is not known when the drug will be given to the woman, although the judgement only allows doctors to give a three-day course of the drug and they have been told they must stop if the woman starts to suffer.
The woman was diagnosed as PVS after she suffered a brain haemorrhage while on holiday in August 2003.
The newspaper said her family wanted her to die with dignity and not live with the disabilities zolpidem might cause.
They are said to be in favour of removing the artificial feeding tube to let her die.
It is not the first time a PVS patient has caused ethical problems.
In 1993, the Law Lords ruled that Hillsborough stadium disaster victim Tony Bland could have his feeding tube removed.
The 22-year-old was crushed and his brain starved of oxygen during the FA Cup semi-final disaster in April 1989, when 95 people died.
For nearly four years he was in a persistent vegetative state.
Doctors at Airedale Hospital in Steeton, West Yorkshire, insisted he would never recover.
His parents fought a legal battle that went to the High Court, the Court of Appeal and finally the House of Lords for the right to lawfully withdraw their son's life-sustaining artificial feeding tube.
The House of Lords ruled that doctors could stop feeding Mr Bland, enabling the hospital to remove the tube without facing charges of murder.
Timothy James, a medical law expert at the University of Central England, said the Bland case established a precedent enabling treatment to be withdrawn.
But he added if doctors could wake up someone they would then be able to ask them what they want.
"It becomes their own decision."
And Dignity in Dying chief executive Deborah Annetts said the decision was deeply troubling as "the human rights of the woman at the centre of this case are being ignored, and she is effectively being treated as a guinea pig".
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