Metoprolol Side Effects: Brand names Toprol, Lopressor. Metoprolol is available in 25 mg, 50 mg and 100 mg immediate release doses and in 25 mg, 50mg, 100 mg and 200 mg ER (extended release) doses. Metoprolol one of a class of drugs called beta-blockers, that block the effects of the beta-adrenergic receptors of the cardiovascular system. It is relatively specific in blocking primarily the beta 1 type of receptors in the heart and blood vessels and has less effect on the beta 2 receptor in the respiratory system, so is called a cardio-selective beta blocker. Many of the metoprolol side effects are predictable based on knowing that stimulation of the beta 1 adrenergic receptors leads to increased heart rate and increased cardiac contractility, while It is also used to reduce death after acute myocardial infarction and to prevent angina pectoris.
Black Box Warnings: AVOID ABRUPT CESSATION. Abrupt cessation of any beta-blocker, including metoprolol, can lead to severe cardiac consequences including acute myocardial infarction, severe exacerbations of angina pectoris and ventricular arrhythmias in angina pectoris patients. All patients should have their dose tapered over 1-2 weeks in case of unrecognized coronary artery disease. and tachycardia.
Common Metoprolol Side Effects: The most common metoprolol side effects are directly related to its function as a beta blocker. Some patients are very sensitive to these effects and bradycardia and resulting hypotension, lightheadedness and fatigue are very common and usually dose related. Other common metoprolol side effects that are common to many beta-blockers include fatigue, depression and dyspnea.
Serious Metopralol Side Effects: Unfortunately although not really common, serious metoprolol side effects are not rare. Some of these serious metoprolol side effects are related to additive effects when used with other medications that can slow AV node conduction like calcium channel blockers, or are in patients with underlying asthma or COPD where metoprolol can lead to increased bronchospasm and sometimes severe respiratory distress. Other severe metoprolol side effects affecting the cardiovascular system include heart block, congestive heart failure, cardiogenic shock when used post MI, severe bradycardia, and Raynaud’s phenomenon. Raynaud’s phenomenon is severe vasoconstriction of peripheral arterioles to the hands and feet on cold exposure. Gangrene has been reported with metoprolol use on very rare occasions. Bronchospasm can occur even in patients without prior known lung disease but is much less common than in those with prior respiratory problems. Hepatitis, photosensitivity, lupus erythematosis, agranulocytosis, and generalized hypersensitivity reactions are other serious reported metoprolol side effects.
Cautions and Drug Interactions: The list of cautions is extensive but the primary theme among them is to take care in using metoprolol in patients with cardiac conduction abnormalities or on other drugs that can affect cardiac conduction, in patients with respiratory disease especially any type of reactive airways disease, and to avoid abrupt withdrawal of metoprolol, especially high dose metoprolol use. Some specific cautions to metoprolol use include AV block, uncompensated CHF, severe peripheral vascular disease, diabetic patients on insulin for fear of masking hypoglycemic reaction symptoms, and patients with underlying bradycardia. See the manufacturer’s prescribing guidelines for more complete and detailed cautions. Drug interactions are numerous, but some of the more commonly used medications with cautions for metoprolol interactions include cimetidine (Tagamet), many opioids, the non-steroidal anti-inflammatory medications, almost all other cardiac and anti-hypertensive medications, many of the SSRI antidepressants, pseudoephedrine, he ergot alkaloids, and almost any potentially vasoconstricting medications. Again for a complete list of drug interactions see the manufacturer’s prescribing guidelines or consult your pharmacist for particular drug interaction concerns.
Unusual Metoprolol Side Effects: Raynaud’s phenomenon and Lupus erythematosis are among the uncommon but unusual side effects of Metoprolol. Most of the metoprolol side effects are class effects of most of the beta-blockers.
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