Metoprolol is a beta blocker, not an ACE inhibitor. Specifically, it is a beta-1 selective (also called “cardioselective”) beta blocker, meaning it primarily targets receptors in the heart rather than in the lungs or blood vessels. Both drug classes are commonly prescribed for high blood pressure and heart conditions, which is why they’re easy to confuse, but they work in fundamentally different ways.
How Metoprolol Works as a Beta Blocker
Your heart has beta-1 receptors on its surface that respond to adrenaline and similar stress hormones. When these receptors are activated, your heart beats faster and harder. Metoprolol blocks those receptors, which slows your heart rate, reduces the force of each beat, and lowers blood pressure as a result.
The “cardioselective” label matters because beta receptors also exist in other parts of your body. Beta-2 receptors in your airways, for example, help keep your bronchial tubes open. Because metoprolol preferentially targets beta-1 receptors in the heart, it is less likely to cause breathing problems than older, non-selective beta blockers. That selectivity has limits, though. At higher doses, metoprolol starts blocking beta-2 receptors as well, which is one reason doctors typically start with a low dose and increase gradually.
How ACE Inhibitors Differ
ACE inhibitors (drugs like lisinopril, enalapril, and ramipril) lower blood pressure through an entirely different system. They block an enzyme that converts a hormone called angiotensin I into angiotensin II. Angiotensin II is a powerful vessel-constricting signal. By preventing its production, ACE inhibitors allow blood vessels to relax and widen, reducing the resistance your heart has to pump against.
In short: beta blockers like metoprolol calm the heart directly, while ACE inhibitors relax the blood vessels. Both lower blood pressure, but they do it from opposite ends of the cardiovascular system. This is actually why the two are sometimes prescribed together, particularly for heart failure. They complement each other rather than duplicating the same effect.
What Metoprolol Is Prescribed For
Metoprolol is FDA-approved for three main conditions: high blood pressure, chest pain from reduced blood flow to the heart (angina), and stable heart failure. It comes in two formulations. The immediate-release version (metoprolol tartrate) is typically taken two or more times per day. The extended-release version (metoprolol succinate) is taken once daily and is the formulation specifically approved for heart failure.
For heart failure, metoprolol succinate reduced the combined rate of death and hospitalization in clinical trials. Notably, most patients in those studies were already taking ACE inhibitors alongside metoprolol, which reflects how the two drug classes are often used as a team rather than as alternatives to each other.
Metoprolol is also widely used off-label for conditions like rapid heart rhythms, migraine prevention, and performance anxiety, all of which benefit from its heart-slowing, adrenaline-blocking effects.
Common Side Effects
Because metoprolol slows the heart and dampens the effects of adrenaline, its most common side effects relate to reduced energy output. Fatigue and tiredness are frequently reported. Dizziness, especially when standing up quickly, can occur because blood pressure drops. Some people notice cold hands and feet, since the drug reduces how forcefully blood is pumped to the extremities.
A slower-than-normal heart rate (bradycardia) is an expected pharmacological effect but can become a problem if the heart slows too much. Weight gain, depression, and sleep disturbances including vivid dreams are less common but well-documented. These side effects are distinct from what you would experience on an ACE inhibitor, where the most characteristic complaint is a persistent dry cough caused by the buildup of certain proteins in the lungs.
Who Should Be Cautious With Metoprolol
Because metoprolol can affect airways at higher concentrations, people with asthma or severe chronic obstructive pulmonary disease need to use it cautiously, if at all. The cardioselectivity that makes metoprolol safer than non-selective beta blockers for the lungs is not absolute, and bronchospasm remains a risk.
People with very slow heart rates, certain types of heart block (where electrical signals in the heart are delayed or disrupted), or very low blood pressure are generally not candidates for metoprolol. The drug should also never be stopped abruptly. Suddenly withdrawing a beta blocker can cause a rebound surge in heart rate and blood pressure, which in some cases triggers chest pain or other cardiac events. Doses are tapered down gradually over one to two weeks.
How Your Body Processes Metoprolol
About 70% of metoprolol is broken down in the liver by a specific enzyme called CYP2D6. This matters because roughly 5 to 10% of people of European descent (and varying percentages in other populations) are “poor metabolizers” who have a less active version of this enzyme. If you’re a poor metabolizer, metoprolol clears your body more slowly, which can make standard doses feel stronger and increase the likelihood of side effects like fatigue or low heart rate.
Other medications that compete for or inhibit that same enzyme can also raise metoprolol levels in your blood. Certain antidepressants and antifungal drugs are common examples. If you’re taking multiple medications, this interaction is worth flagging to your pharmacist. Additional liver enzymes handle a smaller share of metoprolol’s breakdown, so the drug isn’t entirely dependent on one pathway, but CYP2D6 does the heavy lifting.
Beta Blocker vs. ACE Inhibitor: Quick Comparison
- Primary target: Beta blockers act on the heart. ACE inhibitors act on blood vessels.
- How they lower blood pressure: Beta blockers slow heart rate and reduce pumping force. ACE inhibitors relax and widen arteries.
- Signature side effects: Beta blockers commonly cause fatigue and cold extremities. ACE inhibitors commonly cause a dry cough.
- Used together: Yes, frequently. Heart failure guidelines often include both a beta blocker and an ACE inhibitor as part of standard therapy.
- Examples: Beta blockers include metoprolol, atenolol, and carvedilol. ACE inhibitors include lisinopril, enalapril, and ramipril.