How does metoprolol (beta blocker) cause dizziness due to hypotension?

From the Guidelines

Metoprolol causes dizziness primarily by lowering blood pressure and heart rate, leading to reduced blood flow to the brain, especially when changing positions quickly (orthostatic hypotension). As a beta-blocker, metoprolol works by blocking the effects of adrenaline on beta receptors in the heart and blood vessels, which reduces the force and rate of heart contractions 1. This action leads to decreased cardiac output and lower blood pressure, which can result in reduced blood flow to the brain, especially when changing positions quickly. When the brain receives less blood flow than it needs, dizziness occurs as a compensatory response. Additionally, metoprolol can cross the blood-brain barrier and affect the central nervous system directly, contributing to dizziness in some patients.

Some key points to consider when prescribing metoprolol include:

• The usual dose of metoprolol tartrate is 100–200 mg, twice daily, and metoprolol succinate is 50–200 mg, once daily 1
• Avoiding abrupt cessation of metoprolol is crucial, as it can lead to adverse effects 1
• Patients should be aware of the potential for orthostatic hypotension, especially when starting the medication or increasing the dose, and take precautions such as rising slowly from sitting or lying positions and staying well-hydrated 1
• If dizziness is severe or persistent, patients should consult their healthcare provider as dosage adjustments may be necessary

It's also important to note that orthostatic hypotension is a common barrier to intensive blood pressure control, and clinicians should be alert to potential symptoms such as postural unsteadiness, dizziness, or even fainting, especially in older hypertensive patients 1. Lying and standing blood pressures should be obtained periodically in all hypertensive individuals over 50 years old to monitor for orthostatic hypotension.

From the FDA Drug Label

Central Nervous System Tiredness and dizziness have occurred in about 10 of 100 patients. Vertigo, sleep disturbances, hallucinations, headache, dizziness, visual disturbances, confusion, and reduced libido have also been reported, but a drug relationship is not clear Observe patients treated with metoprolol plus a catecholamine depletor for evidence of hypotension or marked bradycardia, which may produce vertigo, syncope, or postural hypotension

Dizziness caused by metoprolol may be related to:

• Hypotension: metoprolol can cause a decrease in blood pressure, leading to dizziness
• Bradycardia: metoprolol can cause a decrease in heart rate, leading to dizziness
• Central Nervous System effects: metoprolol can cause tiredness, vertigo, and other central nervous system effects that may contribute to dizziness 2 However, the exact mechanism of dizziness caused by metoprolol is not clearly established in the provided drug labels.

From the Research

Mechanism of Metoprolol-Induced Dizziness

• Metoprolol, a beta-blocker, can cause dizziness as a side effect, although the exact mechanism is not fully understood 3.
• Beta-blockers, including metoprolol, can cause a decrease in blood pressure, which may lead to dizziness, especially when standing up quickly 4, 5.
• The study of metoprolol's effects on blood pressure and heart rate found that it can cause a significant reduction in systolic and diastolic blood pressure, which may contribute to dizziness 6.

Relationship Between Metoprolol and Orthostatic Hypotension

• Orthostatic hypotension, a condition characterized by a sudden drop in blood pressure when standing up, can cause dizziness and fainting 4, 7.
• While metoprolol is not typically associated with symptomatic postural hypotension, it can still cause a decrease in blood pressure, which may exacerbate orthostatic hypotension in some individuals 5.
• A study found that long-term use of beta-blocker eye drops, including those containing metoprolol, did not significantly increase the risk of falls, dizziness, or orthostatic hypotension in older patients 7.

Clinical Implications

• Metoprolol is generally well-tolerated, but temporary fatigue, dizziness, and headache are among the most frequently reported side effects 3.
• Clinicians should be aware of the potential for metoprolol to cause dizziness, especially in patients with a history of orthostatic hypotension or those taking other medications that can lower blood pressure 4, 5.