Im on toprol (metoprolol). doc said to monitor pulse and be sure it doesn't get to low. how low can it get and still be safe? at which point should i go to er?

50/min: 50/min would be a relatively low pulse. However, in terms of feeling symptoms, it would also be pertinent to get an automatic arm-cuff blood pressure machine and check your blood pressure sitting and standing once or twice/week to ensure a normal pressure while on medication. Lightheadedness might occur if your systolic BP is less than 90mm mercury.

50 beats per min: Generally we aim for a heart rate between 50 and 60 beats per minute. If in the 40's talk to your doctor.