drink a glass of water before you get out of bed the next day. And you should teach yourself to eat whilst both on pills and afterwards.... it makes you feel a lot better generally, but particulalrly helps with low blood pressure. Otherwise, look after yourself generally with vitamins and supplements when you take pills.
I naturally have low blood pressure. When I was younger, my friends used to have to grab for me any time we stood up in school assembly, or I would faint.
I've found that if I don't force myself to eat during and after doing pills, and if i don't regulate the amount of liquids I consume, I'll have quite low blood pressure for about a week afterwards (quite low meaning almost fainting most times that I stand up).
On a couple of occasions I have actually spent most of the next day fainting any time I tried to get up - even just sitting up in bed.
The first time, I tried heaps of things (eg crawling on the ground really slowly, trying to get my boyfriend to hold me up to see if I could stick through it) but ultimately, forcing myself to eat a good meal helpeda bit and then I just had to wait it out. It was pretty scary.. =/
The number of pills you do and what is in the pills is also an important issue.
MDA plays havoc with my blood pressure.