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Metoprolol is an anti-hypertensive (high blood pressure) drug classified as a selective beta-1 receptor blocker, also called a beta adrenergic blocker. Metoprolol is sold under the brand names Lopressor and Toprol-XL and is available in immediate-release and prolonged-release formulations. In addition to high blood pressure, metoprolol is prescribed to treat conditions including angina pectoris (chest pain) abnormal heart rhythms, migraine, tremors, congestive heart failure, bleeding from the esophagus, side effects of antipsychotics, and to prevent second heart attacks.
Beta adrenergic blockers like metoprolol work by blocking certain receptors (beta-1 receptors) for adrenaline. Adrenaline is a hormone that causes increased heart rate and blood pressure, and blocking these particular receptors heart rate and especially blood pressure.
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Side Effects of Metoprolol
For the most part, metoprolol side effects are relatively uncommon, but can be serious. They may include the following:
- fatigue, weakness, drowsiness
- slow heartbeat (bradycardia)
- difficulty breathing or bronchospasm
- depression, anxiety, nervousness, emotional lability (unstable mood)
- confusion, disorientation, short-term memory loss
- strange dreams or sleeping problems
- cold extremities
- nausea, vomiting, diarrhea, or constipation
Metoprolol can worsen the symptoms of the autoimmune disease lupus erythematosus. It interacts with other blood-pressure lowering drugs, oral anti-diabetes medications, and many other drugs. Taking metoprolol with certain migraine drugs (ergot alkaloids) can reduce circulation so dramatically that gangrene in the hands or feet is possible. Patients should tell their health care provider about all the medications and herbal supplements they take.
Smoking changes metoprolol effects, so tell your healthcare provider if you smoke or if you plan on quitting while taking metoprolol. Cocaine reduces the effectiveness of beta blockers including metoprolol.
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Patients should not stop taking metoprolol unless directed by a doctor. If the effects of metoprolol are causing too much trouble, patients should contact their doctor immediately for advice.
Metoprolol generally should not be stopped suddenly. Instead, the dosage should be tapered off over about two weeks. Suddenly stopping the drug can cause chest pain, breathing problems, excessive sweating, and irregular or fast heartbeat. Gradually reducing the dosage is especially important for patients with angina, even if they take metoprolol for a different condition, because stopping the drug abruptly can aggravate angina symptoms.
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"Metoprolol." The Pill Book, 12th Edition, 2006. Harold M. Silverman, Pharm. D., Editor-in-Chief. New York: Bantam Books.