It has worked fine for a few years. In the beginning I was taking a Generic only to suddenly realize it wasn't working and my skipping beats were as active as ever. Upon questioning the Pharmacist, she allowed that LEGALLY, the drug companies only had to put %80 of the active ingredient in the Generic drug! I was put on Toprol and everything was fine until one day my lips began to swell up especially in the morning and then a few weeks later I got a nasty migraine and I never get headaches. I suppose it could be anything but I have my suspicions. The next step is to contact my Cardiologist.