Low blood pressure in Parkinson's disease

I have a T.I.A. stroke last month.
It is related with my parkinson's medication as it causes me low blood pressure. after taking for a long time .I usually have 145/76 normal blood level for the past two years.
The medications cause me with two different blood pressie when you change your body position from sitting to standing or liedown. Your blood pressure would reduce or increase when you are sitting and standing.
Recently I have low blood pressure which is below 100/60 after changing my body position from sitting to standing , rising from sitting or lie -down. It causes me feeling dizzness, vision blurring, and fatique
I understand these syndrome can vary different from person to person.
Kindly brief
Thanks