Depending why you were prescribed Metoprolol, evidently it helped your symptom. Trying to get off it can be an issue if the symptom suddenly came back when you reduced it to 12.5. So Metoprolol was helping and your heart quickly reacted to the reduced dosage. I have a highly allergic reaction to the coating holding the pill together. The pharmacist tried to switch me to different companies making Metoprolol and then to different medications snd nothing worked. My reactions to them was worse than what I got from Metoprolol. So I was placed on 25mgs in the morning and my allergic reaction eased up. It was just a minimum maintenance dosage but it started causing inter reactions with other medications. Causing my heart rate to sink to the upper 40’s and my bp was as low as 51/48. I was getting so lightheaded and dizzy, I said the he!! with this and went off all medications. I was off everything for 5 months when my Tachycardia started to kick in and I had to go back on 25mgs of Metoprolol. I didn’t want to but this morning my bp was 116/68 with a heart rate of 67 and I’m feeling good. So you be the judge, why did my heart seem to start working correctly? Especially after 3 heart attacks since 2018? You could try to switch medications but keep a close eye on your numbers, especially if you have a sudden change. Good luck.