Anyone taking toprol Xl? If so, how much and how is your heart rate on it? I've been on bisoprolol for PVC and migraine and can only tolerate 2.5 mg or else heart rate goes down to 48. The 2.5 mg doesn't last the whole day so doc wants me to try extended release formulation to see if it solves problem. He wants me to start on 25 mg but I think I'm going to only take half to start. I can survive a day with a slightly faster heart rate, but if I take the whole thing and it drops to 48 I'll have to go to the ER.