atrial fibrillation
"I've been on Flecainide 12 years for A-fib but have recently been have more and more episodes.  So my cardiologist also prescribed metoprolol (the smallest dose possible - 1/4 of a 25mg tablet twice daily - due to my being very sensitive to other beta blockers).  My blood pressure dropped (wasn't high in the first place) and my heart rate dropped to the mid/low 40's.  I was also very light-headed, had low energy, some shortness of breath and sometimes nausea.  Discontinued (by doctor) after one week."