My father has been diagnosed with Parkinsonism for more than a decade and recently we came across a medicine/oil which primarily contains cbd (cannabidol – cannabis). Although it hasn’t been prescribed and nor has it been prescribed by our GP.

We’ve heard that it can potentially help ease pain and help him. Is it allowed for us to use cbd oil?

Furthermore, would it be possible to expand on the definition of "if there is no alternative"

by

If the quantity of cannabidol – cannabis in the medicine is negligible, or if he really needs it, then it is okay.