The Health Minister has granted medicinal cannabis be used to treat 20 patients after their doctors applied for a special licence.
The Department of Health grants the licences if the application is endorsed by a consultant who is prepared to monitor its effects.
There have been 43 applications by medical practitioners wanting to prescribe cannabis as a treatment for patients since late 2016.
Licences are valid for three months, followed by six-month extensions to the prescription.
Dr. Des Crowley from the Irish College of General Practitioners said the Government do not want cannabis to become widespread.
He said: "I think that the fear of many including the government is that if you have easy access to cannabis that you have a risk that it may go out to the ... black market.
"There is so much restrictions on how you study the benefits of cannabis that it's difficult to progress it."