Toprol Xl acts mostly blocking beta-adrenoreceptors of the heart and is used to treat hypertension, chest pain (angina), abnormal rhythms of the heart, to treat and prevent myocardial infarction. This medication influences autonomic nervous system which stipulates increased heart rate by blocking its receptors and thus reducing abnormally rapid heart rhythms. It also diminishes myocard irritability, cardiac output and causes other effects.
This medication should be taken with food or just after a meal. Do not chew, squash or break a tablet, drink a glass of water with it. Dosage depends on the treated disease and may vary between 100-450 mg daily. Your individual dosage should be prescribed by your physician. Aged patients are recommended to start from 50 mg daily dose. Kidney failure does not require a dosage correction while liver failure requires usage of other beta-adrenoblockers which are not destructed in liver.
Hypersensitivity to the components of the medication, acute or chronic heart failure, arterial hypotention, congestive heart failure, asthma or other breathing problems, diabetes, disorders of peripheral blood circulation, pregnancy, breast-feeding, depression, liver or kidney disease, a thyroid disorder, or myasthenia gravis.
At the background of common tolerance to the medication among side effects are noticed abdominal cramps, fatigue, insomnia, nausea, depression, memory loss, fever, impotence, lightheadedness, slow heart rate, low blood pressure, cold extremities, sore throat, diarrhea, constipation, and shortness of breath or wheezing. 
Take the forgotten dose when you remember. If your next dose is less than 4 hours away, skip it and return to your schedule. Do not try to compensate a missed dose by taking an extra one.
In case such symptoms of Toprol Xl are noticed: uneven heartbeats, shortness of breath, dizziness, weakness or fainting, bluish-colored fingernails, seek for immediate medical help.
Store between 15-30 C (59-86 F). Protect this drug from moisture and dispensed in tight, keep in a light-resistant container.