What is metoprolol?
Metoprolol belongs to a class of drugs called beta-blockers. It is sold under the brand names Lopressor and Toprol XL, among others. Metoprolol has been available since the early 1980s and has a well-established record for safety and efficacy. It is primarily used to treat high blood pressure (hypertension) and other cardiovascular diseases, such as chest pain (angina) and heart failure.
As of 2017, metoprolol was the sixth most prescribed drug in the USA, with over 68 million prescriptions. Lisinopril (an ACE-inhibitor) and amlodipine (a calcium channel blocker), two of the more commonly prescribed medications, are examples of other antihypertensive drugs that are often prescribed in combination with metoprolol.
Metoprolol is usually taken orally as a tablet, but liquid solutions are available that can be taken orally or administered as injections.
What are metoprolol tartrate and metoprolol succinate?
Of the brand names mentioned in the previous question, Lopressor is the brand name for metoprolol tartrate, while Toprol XL is the brand name metoprolol succinate. Although metoprolol is the active therapeutic agent in both, ‘tartrate’ and ‘succinate’ indicate the salt forms it is converted to.
Many medications are converted into a salt form to improve solubility in water so your body can absorb it more effectively. Metoprolol is different to many drugs, insomuch as the different salt forms affect its therapeutic characteristics.
The most significant difference between the two is that metoprolol tartrate (Lopressor) is only available in immediate-release forms (tablets, injectable, and liquid solution), while metoprolol succinate (Toprol XL) is an extended-release tablet. Both are also available as generic drugs.
While they both have the same active therapeutic agent, the difference in the way each is administered and released into the body means they have some different uses and are dosed differently, which you can read about in the following question: What is metoprolol used for?
What is metoprolol used for?
Both metoprolol tartrate (Lopressor) and metoprolol succinate (Toprol XL) are used to treat:
- High blood pressure
- Chest pain (angina)
Additionally, metoprolol tartrate is used:
- For heart attack, heart disease, and stroke prevention
- To reduce the risk of death after a heart attack (usually with injections)
- To treat an irregular heartbeat (heart arrhythmia)
Metoprolol succinate can be used for:
Metoprolol is often used in combination with other medications, such as ACE inhibitors and calcium channel blockers.
The safety of metoprolol in pediatric patients has not been established and it is not routinely prescribed to children. There is no evidence that patients 65 years old or above respond differently to metoprolol than younger people do, but the relatively small body of evidence means the possibility that they are more sensitive to its effects cannot be completely ruled out. The FDA, therefore, recommends that metoprolol is used with caution in geriatric patients.
How does metoprolol work?
Beta-blockers primarily work by ‘blocking’ adrenergic beta receptors, which prevents adrenaline and noradrenaline from binding to them. Adrenaline and noradrenaline are hormones that increase your heart rate, so blocking them from binding to receptors slows your heart rate down and helps lower your blood pressure.
There are subcategories of beta-blockers, which are primarily differentiated by the parts of the body they work on. Metoprolol is a second-generation or ‘selective’ beta-blocker and acts primarily upon β1 receptors. This means they predominantly affect your heart and, to a lesser extent, your kidneys. Because they do not affect other parts of your body, second-generation beta-blockers may be safer for certain people, such as those living with lung disease.
You can read more about how the different subcategories of beta-blockers work here: Your Most Common Questions About Beta-Blockers Answered
How long does it take for metoprolol to work?
The time it takes for metoprolol to work and the length of time its effects last depend on both the form of metoprolol and the method of intake.
Metoprolol tartrate (Lopressor), when taken orally, usually starts working within an hour and can last for between 6 and 12 hours depending on your dosage, which is why your doctor may instruct you to take metoprolol tartrate two or three times per day. It usually takes around a week of therapy to have the maximum effect.
When injected, metoprolol tartrate begins working almost immediately (within 20 minutes) and can last between 5 and 8 hours.
Because metoprolol succinate (Toprol XL) is an extended-release tablet, it takes longer (around 7 hours) for it to reach peak concentration. The effects last around 24 hours, which is why it is taken once per day. Like metoprolol tartrate, metoprolol succinate usually takes around a week of therapy to have the maximum effect.
What are the side effects of metoprolol?
Metoprolol is usually well tolerated. Like any drug, however, it can cause side effects. Some of the more common side effects include:
- Cold hands or feet
- Fatigue
- Dizziness
- Nausea
- Sleep disturbance
- Constipation
- Sweating
Some of the less common side effects include:
- Depression
- Shortness of breath
- Weight gain
- Swelling in your hands or feet
Side effects are often mild and will go away as your body gets used to the medication. However, if side effects are more severe, persistent, or get worse, you should speak to your doctor as soon as possible.
Allergic reactions to metoprolol are rare but can occur. Signs of a serious allergic reaction should be treated as a medical emergency. They include:
- Skin rash – for example itchy, red, or swollen skin
- Wheezing
- Tightness in the chest or throat
- Trouble breathing or talking
- Swollen mouth, face, lips, tongue, or throat
This is not a comprehensive list of the possible side effects of metoprolol. You should speak to your doctor and read the information label to learn more about the side effects of metoprolol.
Are there other medications that I should not take while taking metoprolol?
There are many other medications with which metoprolol can interact.
Certain antidepressants, including monoamine oxidase inhibitors (MAOIs) and serotonin reuptake inhibitors (SSRIs), can increase the effects of metoprolol and increase the likelihood of side effects. These include MAOIs such as:
- Selegiline (Emsam)
- Isocarboxazid (Marplan)
- Phenelzine (Nardil)
- Tranylcypromine (Parnate)
And SSRIs, including:
Other drugs that can interact with metoprolol include:
- Theophylline (used to treat COPD & asthma)
- Saquinavir (an antiretroviral drug used to treat HIV)
- Alprazolam (Xanax – used to treat anxiety disorders)
- Ibuprofen (an anti-inflammatory painkiller)
- Diphenhydramine (Benadryl – an antihistamine used to treat allergies. The FDA warns that particular care should be taken in patients with a history of allergic conditions, as beta-blockers can increase the severity of anaphylaxis and reduce the effectiveness of epinephrine used to treat an allergic reaction.)
This is far from an extensive list of the drugs that can interact with metoprolol. You should inform your doctor about every medication you take (prescription and over the counter). If the risk of a serious interaction outweighs the benefits of metoprolol, your doctor may consider a different medication.
Similarly, you should inform your doctor of any supplements or herbal remedies you take.
Should I take metoprolol with food?
Food helps your body absorb metoprolol, so your doctor will usually recommend you take it at the same time or times each day, either with or immediately after a meal.
Can I drink alcohol while taking metoprolol?
Alcohol does not directly interact with metoprolol, so it is usually safe to drink in moderation.
However, a possible short-term effect of alcohol – even in small amounts – is lowering your blood pressure. Combined with the therapeutic blood pressure-lowering effects of metoprolol, the risk of side effects such as dizziness or sleepiness may increase.
If this happens, it is recommended that you avoid drinking alcohol while taking metoprolol.
Does metoprolol come with a black box warning?
Black box warnings are the strictest warnings issued by the U.S. Food and Drug Administration (FDA). Black box warnings are issued when there is significant evidence that a drug or product is associated with an adverse reaction that may lead to death or serious injury.
Metoprolol, like other beta-blockers, comes with a black box warning that abrupt cessation of therapy can cause a worsening of angina and, in some cases, a heart attack. The warning states that patients with heart disease are at the biggest risk, but that people taking it only for high blood pressure (hypertension) should also avoid abruptly stopping treatment. According to the warning, patients stopping therapy should slowly reduce the amount they take over a 1-2-week period, based on the advice and under the close supervision of a physician.
You should always take metoprolol exactly as instructed by your doctor.
Is metoprolol safe for pregnant women or nursing mothers?
Studies have shown that metoprolol has adverse effects on pregnant rats when given at a dose equivalent to 11 times the maximum daily dosage for humans. However, no reliable human studies have investigated the effects of metoprolol on pregnant women.
Due to the lack of evidence, most doctors will prescribe an alternative treatment with a more defined safety profile. Metoprolol is normally used only if the benefits of the treatment outweigh the risk of harm to the mother and/or baby, and if no preferable alternative is available.
A small amount of metoprolol is excreted in breast milk. Studies have found that an infant consuming 1 liter of breast milk daily would receive a dose of less than 1 mg of the metoprolol. The FDA recommends that caution should be exercised when metoprolol is prescribed to a nursing mother.
The content on this page is provided for informational purposes only. If you have any questions or concerns about your treatment, you should talk to your doctor, pharmacist, or healthcare professional. This is particularly important if you are taking multiple medications or have any existing medical conditions.
