Here is a collection of user reviews for the medication Toprol XL sorted by most helpful. See User Reviews. Report Problems to the Food and Drug Administration. You are encouraged to report negative side effects of prescription drugs to the FDA.
1 Persistent bad breath or a bad taste in the mouth can also be one of the warning signs of gum disease; which is caused by plaque.  Dry mouth. This occurs when the flow of saliva decreases and can be caused by various medications, salivary gland problems or continuously breathing through the mouth.
1 Bad breath can be caused by surgical wounds after oral surgery, such as tooth removal, or as a result of tooth decay, gum disease or mouth sores.  Other mouth, nose and throat conditions. Bad breath can occasionally stem from small stones that form in the tonsils and are covered with bacteria that produce odor.