Yes, it seems that @jachrist and I are both taking 50 mg Metoprolol Succinate, which is supposed to dispense over a period of time rather than in one "burst" as the tartrate is dispensed. That's what both the Mayo PA and my home cardiologist said when I was experiencing a surgery side effect, and I was switched from the tartrate to the succinate version. BTW, in my case, I do not think it made any difference, the side effect was from another cause. Mine is prescribed to take in the morning. By 3 or 4 in the afternoon I am feeling a bit fatigued, so I plan my day taking that into account.