Metoprolol adverse effects
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Common Adverse Effects of Metoprolol
Metoprolol, a widely used beta-blocker, is associated with several adverse effects, most commonly affecting the cardiovascular and central nervous systems. Frequently reported side effects include dizziness, bradycardia (slow heart rate), hypotension (low blood pressure), lightheadedness, and syncope (fainting) Rafique2024Fux2005Zineh2004+1 MORE. In comparative studies, metoprolol was found to have a lower overall risk of adverse events than diltiazem when used for atrial fibrillation with rapid ventricular rate, though the rates of bradycardia and hypotension were similar between the two drugs .
Central Nervous System and Psychiatric Adverse Effects
Metoprolol can cause central nervous system side effects, particularly in elderly patients. These include confusion, fatigue, nightmares, vivid or bizarre dreams, sleep disturbances, delirium, psychosis, and visual hallucinations Koshy2024Zhao2012Shah2020. Case reports have documented both nightmares and hallucinations in elderly patients, with symptoms resolving after discontinuation of the drug Koshy2024Shah2020. Notably, neuropsychiatric reactions such as acute delirium and psychosis can also occur in younger patients, even at low doses .
Rare and Serious Adverse Reactions
Recent analyses have identified unexpected and serious adverse reactions associated with metoprolol, such as orthostatic intolerance, trigemino-cardiac reflex, decorticate posture, and a strong association with suspected suicide . These findings highlight the importance of ongoing monitoring for rare but potentially severe side effects.
Genetic Factors and Metoprolol Adverse Effects
Metoprolol is primarily metabolized by the CYP2D6 enzyme, and genetic variations in CYP2D6 can affect drug levels in the body. Poor metabolizers of CYP2D6 have higher plasma concentrations of metoprolol, which can increase the risk of bradycardia Fux2005Zineh2004Collett2023. However, most studies have found no significant association between CYP2D6 genotype and the overall frequency of adverse effects, except for a higher incidence of cold extremities and bradycardia in poor metabolizers Rafique2024Fux2005Zineh2004+1 MORE. This suggests that while genetic testing may help identify patients at risk for certain side effects, it does not predict all adverse reactions.
Metoprolol in Special Populations
In patients with chronic obstructive pulmonary disease (COPD), metoprolol did not reduce the risk of COPD exacerbations and was associated with a higher risk of hospitalization for exacerbation . The frequency of side effects was similar to placebo, but caution is advised in this population due to the increased risk of severe respiratory events.
Conclusion
Metoprolol is generally well tolerated, but it can cause a range of adverse effects, most commonly dizziness, bradycardia, hypotension, and central nervous system symptoms such as confusion and vivid dreams. Rare but serious reactions, including psychiatric symptoms and suspected suicide, have also been reported. Genetic differences in CYP2D6 metabolism may increase the risk of bradycardia but do not account for all adverse effects. Continuous monitoring and individualized care are important, especially for elderly patients and those with comorbid conditions.
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