What Is Metoprolol and What Is It For?

Metoprolol is a medicine often used to treat high blood pressure. Let's know other of its uses, contraindications and what doses the experts recommend for its intake.

Known under the trade names Lopressor, Tropol, or Tropol XL, metoprolol is a drug used to treat cardiovascular disease. It’s approved by the Food and Drug Administration (FDA) and the European Medicines Agency (EMA). It has quick-release and time-release versions.

The drug can be used alone or in the company of others and is part of the group of beta blockers. All the drugs in this group work by relaxing the blood vessels, reducing the heart rate and thereby relieving the strain on the heart. Let’s see what it’s used for, its contraindications, dosage, and how to store it.

What is metoprolol used for?

Metoprolol is a beta-adrenergic receptor-blocking agent. Although in low or medium doses it has a preferential effect on beta 1 adrenoceptors (located in the heart muscle), in high doses it also inhibits beta 2 adrenoceptors (located in the vascular and bronchial musculature).

We know that after its ingestion it disintegrates into small granules that act as independent cells that release the drug. This release is constant and on average lasts around 20-24 hours. It’s a drug that’s very well tolerated by patients, whose treatment begins in low doses that then increase over the following weeks.

The properties of the drug are used for the following conditions:

Arterial hypertension

Multiple studies and investigations have supported the use of metoprolol as a drug to treat high blood pressure. Its use dates back to the mid-1970s due to its dilating effect on blood vessels, although this is a bit slower than other drugs in the same class.

It’s often used in the company of other agents (such as diuretics), with the goal of minimizing the side effects of high blood pressure. Its use continues today under these trade names.

Angina pectoris

The drug has also been shown through trials and tests to be effective in counteracting the symptoms of angina pectoris. In fact, this is its second most common use.

Angina pectoris is characterized by a sharp pain caused by decreased blood supply to the heart muscle. Coronary artery disease is often the main cause of angina.

Myocardial infarction

Metoprolol alone has also been shown to reduce the chances of a heart attack. This is its most frequent use, although it can also be used as a treatment after the patient has experienced an attack. Some studies suggest that the reduction in heart attacks can be up to 36%.

These are the three most common uses of the drug. However, and in certain circumstances, it can also be used as a treatment for palpitations in the absence of heart disease, migraine prophylaxis, adjuvant to thyrotoxicosis and for cardiac arrhythmias.

Contraindications of metoprolol

Despite the versatility of the drug, it’s subject to several contraindications. Following the bulletins of the Food and Drug Administration, the use of metoprolol should be avoided in the following cases:

• Hypertension and angina: It’s contraindicated in the presence of sinus bradycardia, major first-degree heart block, overt heart failure, and cardiogenic shock.
• Myocardial infarction: Not recommended for patients with a heart rate of less than 45 beats per minute, second or third-degree heart blocks, or systolic blood pressure less than 100 mmHg.

Its use isn’t recommended in people suffering from sick sinus syndrome, peripheral arterial disease with risk of gangrene, and patients with inotropic treatment that acts as an agonist with beta receptors.

If you suffer from diabetes, hypoglycemia, pheochromocytoma or hypotension, its use should be avoided. On the other hand, care must be taken if there’s hypersensitivity or allergy to the drug component. If there’s a history of both in the intake of other beta-blockers, their administration should be carried out with caution.

Evidence also indicates that it’s contraindicated during pregnancy and lactation. In addition to this, care must be taken with the interaction of the drug with other drugs. Its ingestion should be avoided in the presence of barbiturates, propafenone, and verapamil.

In turn, the doctor may have to adjust the dose in the presence of amiodarone, class I antiarrhythmics, non-steroidal anti-inflammatory drugs, digitalis glycosides, diphenhydramine, adrenaline, clonidine, quinidine, and rifampin, among others.

Side effects of taking metoprolol

According to the European Medicines Agency (EMA), 10% of patients develop adverse effects. Usually, this is due to the dose delivered. Among the main collateral effects we find the following:

• General: Weight gain and fatigue.
• Cardiac: Bradycardia and palpitations. Less common are chest pain and cardiac arrhythmias.
• Nervous system: Dizziness and headaches.
• Eye: Dryness and irritation. Conjunctivitis is a rare side effect in patients.
• Respiratory: Dyspnea and other asthma symptoms.
• Gastrointestinal: Diarrhea, constipation, vomiting, nausea, and abdominal pain.
• Vascular: A cold sensation in hands and feet. Syncope is a very rare side effect.
• Psychiatric: Nightmares, sleep disturbances, and depression. These three are not frequent.

Another relatively common side effect is drowsiness. For this reason, you must be careful after taking it, especially if you work in a work environment where you always have to be alert.

If you experience an allergic reaction it will usually manifest itself through hives and rashes. If you present this and other problems, you should contact the specialist in search of a possible dose adjustment.

The recommended dose of metoprolol

The dose is administered according to the condition to be treated, its severity, and the characteristics of the patient (weight, age, height, underlying diseases, intake of other medications, and so on). Based on the EMA bulletin cited in the previous section, the most used doses depending on the case are the following:

• High blood pressure: Between 100 and 200 milligrams a day. It can be carried out with a single intake or divided into two doses a day. If the expected results aren’t obtained, it’s suggested to combine metoprolol with diuretics or calcium antagonists.
• Angina pectoris: Usually given two intakes of 100 or 200 milligrams. It can be combined with nitrates if necessary.
• Cardiac arrhythmias: Two or three doses of 100 or 200 milligrams are given during the day. The dose can be increased according to the criteria of the specialist.
• Myocardial infarction: 50 milligrams every 6 hours 15 minutes after the first injection. These will continue for two days, after which the drug can be continued in tablet form.
• Migraines: Between 100 and 200 milligrams always divided into two doses during the day.
• Palpitations: When there are palpitations with no heart disease, the doctor will usually prescribe 100 milligrams in a single dose, preferably in the morning.
• Thyrotoxicosis: This is adjusted according to the needs of the patient, although preferably it begins with a dose of 50 milligrams three times during the day. It can be increased to a maximum of 100 milligrams.

Final recommendations

If possible, metoprolol should be taken on an empty stomach, thus enhancing the assimilation in the body. However, the doctor’s instructions should be followed as appropriate. The drug is stored in its container at a temperature between 15 and 30 degrees Celsius (60 to 86 F). Compounds must be hermetically sealed.

Remember that you shouldn’t start to take it without the supervision of a specialist. If you suspect that you may be suffering from any of the diseases outlined above, seek medical assistance to make an accurate diagnosis, rule out other conditions, and adjust the dose depending on the case.