I take a form of cardizem called Tiazac (actually its generic called taztia) 180 mg. It did lower my heartrate along with my blood pressure. I think it started working within a week. I don't remember what my unmedicated heartrate was, I think in the 80s. I take taztia and clonidine and my heartrate is in the upper 50s and 60s.

Taztia gave me a bit of constipation, which I could mostly take care of by taking the drug after breakfast and not before. At first I would also experience a feeling of strong heartbeats, but that has gone away. I also have ringing in my ears, which is varying - sometimes rather annoying, other times hardly noticable.

I actually wonder now if the ringing is louder when my pressure is lower, and almost gone when my pressure is higher (120-135/70-75 range).

You don't have to wean, you can just stop taking it.