Toprol (metoprol
XL) is a beta blocker which is prescribed
in a number of different situations (heart failure, arrhtyhmias, high blood pressure, etc). Without knowing your medical history and being able to perform a physical examination, there is no way of knowing for sure what is going on. However, Toprol is a long-acting beta blocker, so even missing a dose for 5 hours, should theoretically not bring the acute onset of any symptoms.