Doctors will be able to prescribe cannabis products to patients from next month Home Secretary Sajid Javid has announced.
The new rules apply to England, Wales and Scotland, and follow several high-profile cases, including that of young epilepsy sufferers Alfie Dingley and Billy Caldwell, whose conditions appeared to be helped by cannabis oil.
Setting out the new regulations regarding cannabis-based products for medicinal use, Mr Javid said: "This brings these products explicitly into the existing medicines framework.
"These regulations are not an end in themselves. The ACMD (Advisory Council on the Misuse of Drugs) will be conducting a long-term review of cannabis and the National Institute for Health and Care Excellence (Nice) has been commissioned to provide advice for clinicians by October next year.
"The Government will monitor the impact of the policy closely as the evidence base develops and review when the ACMD provides its final advice."
Alfie's mother, Hannah Deacon, said: "Today is a momentous day for every patient and family with a suffering child who wish to access medicinal cannabis.
"We urge the medical world to get behind these reforms so they can help the tens of thousands of people who are in urgent need of help.
"I have personally seen how my son's life has changed due to the medical cannabis he is now prescribed.
"As a family we were facing his death. Now we are facing his life, full of joy and hope, which is something I wish for each and every person in this country who could benefit from this medicine."