The new NHS guidelines say that prescriptions are only likely to be prescribed for adults with vomiting or nausea caused by chemotherapy, muscle stiffness caused by multiple sclerosis and for children with rare and severe forms of epilespy.
The list doesn't include chronic pain, however, which is thought to be one of the main drivers for medicinal use of cannabis.
The letter goes on to say that prescribers should only prescribe a product "where they are certain of its content and quality". Two of the main reasons people use cannabis is for anxiety and depression, and they're not likely to be under consultant care.
Cannabis-derived medicinal products are now available on prescription in England, Wales and Scotland.
The Advisory Council on the Misuse of Drugs (ACMD), which carried out the second part of the review, then said doctors should be able to prescribe medicinal cannabis provided products meet safety standards.
The decision to prescribe the medicine will be made on a case-by-case basis, and "only when the patient has an unmet special clinical need that can not be met by licensed products".
If they can not find a specials supplier who is able to fill the order, the PSNC spokesperson said, the pharmacy team should "get in touch with the prescriber to try and resolve the situation, which may require them to advise the patient to obtain the medicine via another route".
"Specialist doctors will have the option to prescribe these products where there is a real need".
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Cannabis-based products for medicinal use will not be available from General Practitioners.
"Meanwhile we've got to get on with making as many people who need it get medicine from cannabis as soon as possible".
Other bodies have released their own guidance in response to the legislative change.
This news comes after a tiresome campaign from parents including Charlotte Caldwell, whose son Billy suffers from severe epilepsy.
But what does this mean for others who could benefit from its medical use.
The Royal Pharmaceutical Society (RPS) has welcomed the change in legislation.
The Home Secretary has made it clear that the legalisation of medicinal cannabis does not pave the way towards legalising cannabis for recreational use.
"The move will also make it easier for research into these products to take place", he added.