... resting heartbeat is usually around 125. My rheumatologist decreased Prednisone to 5mg and said my heart would give out in a few years if the dosage was not lowered to 5mg. I started taking metoprolol about a week ago. No problematic side effects so far and it has helped a little already. I take 25mg and will increase to 50. How will the side effects increase as the dosage increases?