The debate about the status of medicinal marijuana in WA has taken another turn - with Health Minister Kim Hames writing to a frustrated Perth mum to say it can be prescribed but the substance itself is proving inaccessible.

Amalia's 10-year-old daughter suffers from a rare and severe form of epilepsy known as Dravet Syndrome and has been hospitalised since Saturday night after a seizure.

CBD was effectively legalised in WA from June 1 but is yet to be approved by the TGA.

She has tried 23 forms of traditional drugs without great success - and is currently on a combination of four - and Amalia was keen to trial the use of the compound cannabidiol (CBD).

She was delighted to receive a letter from Dr Hames saying that as of "June 1, 2015, CBD can be supplied, obtained and used, in the same way as any other prescription medicine."