I too had high blood pressure, first diagnosed when I was about 29 and only 25 lbs overweight.

Atkins has helped me get into a "healthy" blood pressure range and I was able to stop taking medicine. I sometimes wonder if the "healthy" range is really ideal, or if that is something pushed by pharmaceutical company research to sell more medicine, but that is beside the point.

I quit my medicine before low carbing, though I wouldn't necessarily recommend that. My blood pressure dropped fairly fast when I went below 20 grams of carbs per day for my 2 week induction. I sorta worried that if I did induction while taking a medicine that was designed to eliminate sodium from my body that I would really be thrown off balance electrolyte wise.

I think "Protein Power" had some good suggestions for how to approach reduction in BP medicine while low carbing, but I can't remember what was specifically said.