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

From the Guidelines

Metoprolol causes dizziness primarily through its effects on blood pressure and heart rate, leading to decreased cardiac output and lowered blood pressure, which can result in orthostatic hypotension and reduced blood flow to the brain. As a beta-blocker, metoprolol works by blocking the effects of adrenaline on beta receptors in the heart and blood vessels, which slows heart rate and reduces the force of heart contractions. This mechanism is supported by the 2008 ESC guidelines for the diagnosis and treatment of acute and chronic heart failure, which notes that beta-blockers like metoprolol can cause symptomatic hypotension, including dizziness 1.

When blood pressure drops too much or too quickly, especially when changing positions, less blood flows to the brain, resulting in dizziness. Additionally, metoprolol crosses the blood-brain barrier and can directly affect the central nervous system, contributing to dizziness as a side effect. The medication can also cause changes in blood sugar levels in some patients, which may lead to dizziness if blood sugar drops too low.

Some key points to consider when prescribing metoprolol include:

• Monitoring patients for signs of orthostatic hypotension, such as dizziness or lightheadedness, especially when changing positions
• Adjusting the dose of metoprolol based on patient response and tolerance, as recommended in the 2007 ACC/AHA guidelines for the management of patients with unstable angina/non-ST-elevation myocardial infarction 1
• Considering alternative beta-blockers or adjusting the treatment plan if patients experience persistent or severe dizziness
• Educating patients on how to manage dizziness, such as changing positions slowly and staying hydrated, as noted in the seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure 1

Overall, the most effective way to manage metoprolol-induced dizziness is to monitor patients closely, adjust the dose as needed, and educate patients on how to manage symptoms, as supported by the highest quality and most recent evidence 1.

From the FDA Drug Label

Catecholamine-depleting drugs (e. g., reserpine) may have an additive effect when given with beta-blocking agents, or monoamine oxidase (MAO) inhibitors. 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 its effects on the cardiovascular system, particularly hypotension and bradycardia.
• The combination of metoprolol with other medications, such as catecholamine-depleting drugs, may increase the risk of dizziness due to additive effects on blood pressure and heart rate.
• The exact mechanism of metoprolol-induced dizziness is not explicitly stated in the drug label, but it is likely related to its beta-blocking activity and subsequent effects on the cardiovascular system 2.

From the Research

Mechanism of Dizziness Caused by Metoprolol

• Metoprolol is a beta-blocker that can cause dizziness as a side effect, as reported in a study published in 1986 3.
• The exact mechanism of dizziness caused by metoprolol is not fully understood, but it may be related to its effects on blood pressure and heart rate.
• A study published in 1982 found that metoprolol reduces cardiac output by slowing heart rate, which may contribute to dizziness 4.
• Another study published in 2011 found that metoprolol impairs resistance artery function in mice, which may also contribute to dizziness 5.

Hemodynamic Effects of Metoprolol

• Metoprolol has been shown to reduce mean arterial blood pressure and heart rate in patients with essential hypertension 6.
• The reduction in cardiac output caused by metoprolol is not related to decreased cardiac performance, but rather to the decrease in heart rate 4.
• Metoprolol has also been shown to increase systemic vascular resistance, which may contribute to its effects on blood pressure and dizziness 4.

Pharmacokinetics of Metoprolol

• The pharmacokinetics of metoprolol have been studied extensively, and it has been found to have a dose-dependent increase in maximum plasma concentration and area under the concentration-time curve 7.
• Metoprolol is metabolized by the liver and excreted by the kidneys, and its pharmacokinetics may be affected by renal and hepatic impairment 7.
• The pharmacokinetics of metoprolol may also be affected by drug-drug interactions and food intake, which may contribute to its effects on dizziness 7.