Metoprolol is a widely used beta-blocker that can interact with several other drugs in documented, clinically important ways. According to FDA drug labeling and clinical references, the most significant interactions occur with CYP2D6-inhibiting drugs (which can double metoprolol levels in your blood), certain heart medications like verapamil and clonidine, and epinephrine (which may become less effective during an allergic emergency). This guide explains the documented interactions sourced from FDA labeling and clinical literature, what they mean for your health, and what questions to ask your pharmacist or doctor.
Metoprolol is a beta-blocker—a class of medications that work by slowing heart rate, reducing the force of heart contractions, and lowering blood pressure. Beta-blockers accomplish this by blocking the effects of epinephrine and norepinephrine on the heart and blood vessels. Metoprolol is typically prescribed to treat high blood pressure, angina (chest pain), heart failure, and to reduce the risk of heart attack and stroke.
Like all medications, metoprolol is processed (metabolized) by your body, primarily through an enzyme called CYP2D6 in the liver. This metabolic pathway is crucial to understanding many of metoprolol's interactions: drugs that inhibit CYP2D6 can slow the breakdown of metoprolol, causing it to accumulate in your bloodstream. Other interactions occur because metoprolol's effects on heart rate and blood pressure can combine unpredictably with other cardiac or blood-pressure-altering medications.
According to the FDA drug label for rifampin, one of the most concerning interactions is between metoprolol and rifampin—an antibiotic used to treat tuberculosis and certain infections. Rifampin causes a dramatic decrease in metoprolol exposure: the amount of metoprolol circulating in your blood can drop significantly because rifampin speeds up the enzyme activity that breaks metoprolol down.
The practical consequence is that if you are taking both drugs, your metoprolol dose may become ineffective at controlling your heart rate, blood pressure, or angina. However, the FDA source record does not specify a particular mechanism or dose adjustment recommendation for this specific pair. If you require both metoprolol and rifampin, close monitoring of your blood pressure and heart rate by your physician is essential, and your metoprolol dose may need to be increased.
Several common medications are strong inhibitors of the CYP2D6 enzyme. When you take these drugs together with metoprolol, the metabolism of metoprolol slows, and its concentration in your blood can nearly double. According to FDA and NLM clinical data, this increases the risk of excessive beta-blockade—meaning your heart rate may drop too low, your blood pressure may fall too much, or you may experience dizziness and fatigue.
The documented CYP2D6 inhibitors that interact significantly with metoprolol include:
When any of these drugs are used with metoprolol, source records indicate that close monitoring is required. Your pharmacist or physician may need to adjust your metoprolol dose downward or monitor your heart rate and blood pressure more frequently. Do not stop or change your dose without medical guidance.
Verapamil is a calcium-channel blocker commonly used to treat high blood pressure and certain heart rhythm problems. According to clinical references, when metoprolol and verapamil are combined, verapamil's ability to clear metoprolol from the body is reduced. This causes a buildup of metoprolol and, more importantly, creates additive negative effects on heart rate and AV conduction (the electrical conduction through the heart). Both drugs slow the heart; together, they can slow it too much, leading to dangerously slow heart rates or conduction blockade. Close monitoring of heart rate, blood pressure, and sometimes an electrocardiogram (ECG) is warranted if this combination is necessary.
Clonidine is a blood-pressure-lowering medication that works differently than beta-blockers—it reduces norepinephrine release from nerve endings. When combined with metoprolol, an additive negative chronotropic effect (combined heart-rate-slowing effect) can occur, increasing the risk of bradycardia (slow heart rate) and potentially causing dizziness, syncope (fainting), or vertigo. There is also an important special consideration: if a patient taking both drugs needs to discontinue clonidine, the beta-blocker should be withdrawn several days before the gradual withdrawal of clonidine. Abrupt clonidine withdrawal can cause a dangerous rebound hypertension (sudden increase in blood pressure), and the beta-blocker could worsen this rebound. Always discuss any planned medication changes with your physician.
Reserpine is an older blood-pressure medication that works by depleting catecholamines (epinephrine and norepinephrine) from nerve terminals. When combined with metoprolol—which also has sympathetic-depressant effects—the cumulative effect can be substantial. The documented interaction warns of additive catecholamine depletion, potentially causing hypotension (low blood pressure), marked bradycardia, vertigo, syncope, or postural hypotension (dizziness on standing). This combination requires careful clinical judgment and close monitoring.
One of the most clinically important and sometimes overlooked interactions documented in the metoprolol FDA label involves epinephrine. Beta-blockers, including metoprolol, can reduce the body's responsiveness to epinephrine. This is particularly dangerous in an emergency setting.
If you have a severe allergic reaction (anaphylaxis) while taking metoprolol, the usual doses of epinephrine that would normally reverse the reaction may be less effective or ineffective. Additionally, patients with a history of severe anaphylactic reactions may be more reactive to a repeated allergen challenge while taking a beta-blocker. This does not mean you should stop taking metoprolol if it is medically necessary, but it is critical that anyone prescribing epinephrine (such as during an emergency room visit, or when filling an epinephrine auto-injector prescription) be aware that you are taking a beta-blocker. Higher doses of epinephrine or alternative vasopressor agents may be needed.
Beyond the interactions discussed above, the source records also note that metoprolol may interact with other drug classes, though the specific clinical consequences are less detailed:
If you are taking any other cardiac medications, antiarrhythmics, antidepressants, or blood-pressure drugs, review the complete list with your pharmacist to identify potential interactions not detailed in this guide.
The interactions presented here are drawn from FDA-approved drug labels (particularly the rifampin and metoprolol tartrate labels) and NLM/NIH clinical reference sources. These are the most authoritative sources for drug safety information available to the public. When a source record does not specify a mechanism or particular dose adjustment, we note that limitation rather than inventing clinical guidance. Your pharmacist and physician have access to the same source data and can provide personalized recommendations based on your full medical history.
To illustrate how a CYP2D6 inhibitor interaction might unfold, consider this hypothetical example:
A patient is taking metoprolol 50 mg twice daily for high blood pressure, and their blood pressure and heart rate are well controlled. Their physician prescribes fluoxetine 20 mg daily for depression. Fluoxetine is a strong CYP2D6 inhibitor. After 1–2 weeks of taking both drugs together, the patient begins to feel unusually tired, their heart rate drops from a baseline of 65 beats per minute to 55, and they feel lightheaded when standing up. These signs suggest that metoprolol is accumulating in their blood because fluoxetine is slowing its breakdown. In this hypothetical scenario, the physician might order an ECG, check blood pressure more frequently, and potentially reduce the metoprolol dose from 50 mg to 25 mg twice daily until the balance is reestablished. (This is a hypothetical example only; your actual dose adjustments must be made by your physician.)
A hypothetical second example: A patient is on metoprolol for atrial fibrillation (irregular heart rhythm). A cardiologist adds verapamil because the patient's heart rate is not controlled well enough. Within days, the patient notices that their resting heart rate has dropped from 75 to 52 beats per minute, and they feel fatigued. An ECG shows a prolonged PR interval (a sign of slowed electrical conduction through the heart). This hypothetical scenario illustrates the documented additive negative effects on heart rate and AV conduction. The physician might reduce one or both drug doses, or monitor the patient more closely. Again, this is hypothetical and illustrates the principle; actual management depends on the individual patient's condition.
Before filling a prescription for metoprolol or adding a new medication to your regimen if you are already taking metoprolol, consider asking:
The interactions described in this guide are sourced from authoritative FDA and NIH/NLM databases, but they represent only a portion of documented drug interactions. To ensure you have identified all relevant interactions between your medications, visit checkdruginteractions.com and enter your complete medication list. Always confirm any medication decisions—starting, stopping, adjusting doses, or adding new drugs—with your pharmacist or physician. They can review your individual health history, current medications, and medical conditions to make personalized recommendations. If you are taking metoprolol and believe you may be experiencing symptoms of an interaction (such as unusually slow heart rate, severe fatigue, or dizziness), contact your healthcare provider promptly.
CDI checks every pair across up to 20 drugs — backed by FDA and NIH data.
Drug interaction data sourced from U.S. FDA drug labeling via openFDA and the U.S. National Library of Medicine (NLM), National Institutes of Health. For informational purposes only. Always consult your pharmacist or physician before making any medication decisions.
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