@dirko Good point! However, and this also is based on many reports by patients across fora, metoprolol has an incremental effect on the heart to the point where suddenly patients report feeling dizzy, out of breath, or they fall after fainting, and it is soon found that their dose of metoprolol is now too high and that their hearts are being beaten down to dangerous rates. This is especially the case for patients whose arrhythmia, such as atrial fibrillation, is intermittent, or paroxysmal, and whose hearts spend a lot of time in normal sinus rhythm. It is during these periods that the heart can be medicated overly and have its output reduced to the point where it is dangerous. A few learn this the hard way.