Sajid Javid allowed 12-year-old Billy Caldwell one of the bottles of cannabis oil confiscated at Heathrow Airport on Monday after his mum tried to bring them into the UK from Canada.
Charlotte Caldwell, of Castlederg in Co Tyrone, Northern Ireland, said the youngster was showing signs of improvement after receiving three doses of the drug at Chelsea and Westminster Hospital.
She now wants the law changed so other children with similar conditions can get the drugs.
An emergency treatment licence, invoked by Mr Javis on Saturday, grants Billy about 20 days’ treatment, but Ms Caldwell says she is confident he will get the rest of the drugs.
A senior clinician can apply for a longer licence when he has recovered sufficiently to be seen by neurologists.
Ms Caldwell said it had been “absolutely horrific” and “cruel” that Billy had been refused the cannabis oil.
She urged the Home Secretary to authorise the release of the rest of his six-month supply and told Sky News she would not leave London until Mr Javid had met her.
Ms Caldwell said: “This experience that myself and my little boy have endured in this last week has been horrendous, I do not want, and I will not stand by and let, any other family in our country endure it. It’s absolutely horrific, it’s cruel.
“I want nobody in Government, and nobody who has been impacted by massively outdated laws, to be under any impression that this is job done. This is just the start.
“The energy we’ve brought to Billy’s campaign is as nothing compared to what we are prepared to unleash to drive complete reform.
“I want to meet the Home Secretary and Health Secretary, urgently, this week, to get assurance that not only will Billy’s meds never again be removed, but to call for an urgent review of the overall policy on medical cannabis as it affects everyone who could benefit.”
Mr Javid said he had used “an exceptional power” to “urgently issue” a licence to treat Billy with cannabis oil.
Ms Caldwell says the oil is keeping the boy’s seizures at bay and he had been free of seizures for more than 300 days while using it previously.
She said: “We have experts at Chelsea and Westminster who have seen the improvement in Billy.
“This is a medical, clinical decision to use it. It is not a decision to be taken by bureaucrats and politicians. They are not qualified to take that decision.”
Former drugs minister Norman Baker has described the confiscation of the oil as “cruel and inhumane”, and repeated his calls for the law to be changed.
Mr Baker said: “It became very clear to me in my time as drugs minister that cannabis has useful medical properties and, indeed, that it is the only substance that works for some people, a situation widely recognised in other countries.”