Has anyone been switched form Toprol XL to Lopressor?

Hi my name is Nicole, 21 yrs old. My general practitioner refilled my generic toprol xl as generic lopressor without informing me of the change. This was supposedly due to a pill shortage and I had to figure it out on my own. I'm just wondering if anyone has been switched from toprol xl to lopressor and if so what kind of side effects, if any, have you had? I was taking toprol xl 25 mg in the am and 12.5 in the evening, and continued to do the same thing with the generic lopressor. Unfortunately for me, this was NOT the same, b/c the lopressor only lasts 10-12 hours and I was getting breakthrough tachycardia quite often. Thanks for any input!

[Encephalomalcia]

Metoprolol is the generic used for Lopressor and Troprol XL.  Coreg is another beta blocker that blocks more receptors.