Charlotte Caldwell attempted to bring medicinal cannabis oil into the UK for her 12-year-old son Billy, but it was confiscated at Heathrow airport on Monday after a flight from Canada.
He was taken to Chelsea and Westminster Hospital on Friday after a “sudden increase in frequency and intensity of seizures”, his family said.
Speaking outside the London hospital, Ms Caldwell said her son’s “brutal condition” had “returned with a vengeance” since the medication was confiscated.
“These seizures are life-threatening,” she told Sky News.
“One seizure could kill him.
“I’m absolutely devastated that we’re back to where we were nearly two years ago before medicinal cannabis.
“He’s a beautiful, sweet, innocent wee boy who doesn’t deserve this callous treatment.”
Ms Caldwell said she believed the confiscated treatment had been moved to the Home Office and appealed to staff there to show “compassion” and bring it to the hospital.
Billy, from County Tyrone in Northern Ireland, was given a prescription for medicinal cannabis oil last year to help treat his epilepsy – the first time the drug had been prescribed by the NHS.
But the boy’s doctor was told by Home Office drug enforcement teams to stop prescribing the medication, which Ms Caldwell credits with keeping her son’s seizures at bay.
In a statement, Billy’s family said he is now too ill to travel back to Canada for treatment.
“The situation is now described by doctors in Canada and Northern Ireland familiar with Billy’s case as being life-threatening,” they said.
His “increasingly concerned” mother initially took him to St Mary’s Hospital in London on Thursday night, where doctors were “horrified” that he was being deprived of the treatment, their statement added.
Billy, who is also autistic, with pronounced communication difficulties, then suffered back-to-back seizures on Friday after being seizure-free for more than 300 days when he was previously given the cannabis oil, according to his family.
Ms Caldwell said: “This is beyond cruelty.
“We’ve now reached the point where Billy is too ill to travel to get his medication, but his medication is stored minutes away from where we’re now living in London.
“Despite the best and honest efforts of the NHS, frontline doctors are fighting Billy’s condition with both hands tied behind their back because the only medication that will be effective is the cannabis oil with CBD and THC.
“Those meds need to be released immediately.”
After arriving at Heathrow on Monday, she met Home Office Minister Nick Hurd. She said she asked the MP for the medicines to be returned, but was refused.
“We will not stop, we are not going to give up,” she said after the medicine was seized.
“We have love, hope, faith for our kids and we are going to continue.”