Suggest Remedy For Severe Pain From Nerve Damage Associated With Shingles

My mother suffers chronic severe pain from nerve damage associated with shingles. We have tried everything to relieve her pain but nothing has worked. She is unable to take oral pain killers as they make her very dizzy and nauseous. We have been hearing in the news etc lately that medicinal cannabis is an effective pain reliever. Is there any way that we can get access to this to try it in Australia. We live in Sydney. Kay