I take a beta blocker not so much for high blood pressure, but rather that I have a mostly blocked cardiac artery that they can't get a stent into. If my heart rate get above 170, I have chest pain and could have another heart attack.

Beta blockers work by lowering the heart rate. This is bad for cycling for a couple of reasons. (1) Lower heart rate means you can't move as much oxygen to the muscles and brain. (2) Lower heart rate means that you can't cool your core body as well as blood flow is what does a lot of this.

Also BBs are used to treat anxiety disorders! I read recently that some performers and public speakers use them to calm themselves before going on stage. I know that things which would have bothered me at work didn't bother me at all after taking the BBs.

Like another poster, I'm on 1/4th of the original dosage which is an improvement. Still if I'm riding with someone about my age and fitness level, my heart rate is often 10-20 BPM less. BTW: I wear a heart rate monitor while cycling and have it beep at anything more than 160 BPM.

If you are on BB for just blood pressure I would highly recommend talking to your doctor to see if there are other options as BBs do mess up your riding.

Oh! I found out this the hard way: If you have gout do NOT let them put you on a diuretic. The diuretic dropped my BP like a rock, but I started having frequent gout attacks.