Metoprolol – a beta blocker

The beta-blocker metoprolol is used to treat  high blood pressure , certain  cardiac arrhythmias , coronary artery disease, and for the acute and long-term treatment of a heart attack. In addition, the active ingredient can also be used to prevent migraine attacks. Side effects such as tiredness, dizziness and headaches can occur while taking metoprolol. In rare cases, there may also be a sharp drop in blood pressure or a significant decrease in heart rate. Find out more about the effects, side effects and dosage of metoprolol here.

The active ingredient metoprolol

Metoprolol belongs to the group of  beta blockers.  The active substance blocks the so-called beta-1 receptors in the body, to which messenger substances such as  adrenaline  and noradrenaline normally bind. Metoprolol weakens their effect, causing a reduction in blood pressure, heart rate, stroke volume and conduction speed. 

What does metoprolol work against?

 Metoprolol is prescribed to treat high blood pressure similar to  ramipril  or  amlodipine . The fact that the active ingredient also leads to a protection of the heart, it is also used to relieve the heart after a  heart attack  and to prevent heart attacks. It is also suitable for the treatment of tachycardic cardiac arrhythmias (palpitations), weak  cardiac insufficiency  or coronary heart disease.

In addition, metoprolol is also used to prevent migraine attacks. According to current knowledge, the blood vessels in the meninges are greatly expanded during a migraine attack. Taking metoprolol causes the vessels to narrow and the symptoms are relieved as a result.

Side effects of metoprolol

Taking metoprolol can be associated with a variety of side effects. At the beginning,  central nervous disorders  can occur, such as:

Occasionally, side effects in the  gastrointestinal area  such as  diarrhea  and  constipation  as well as nausea and vomiting can be caused.

Skin rashes, reddening of the skin and itching were also occasionally   observed.

In addition, side effects such as muscle weakness and muscle cramps and discomfort in the limbs can occur. 

Metoprolol: Rare side effects

In rare cases, taking metoprolol can also cause more serious side effects. These include, among other things:

  • a sharp drop in blood pressure
  • a sharp drop in heart rate
  • palpitations
  • an increase in myocardial insufficiency
  • Disorders of the excitation conduction
  • shortness of breath on exertion

For a detailed overview of all side effects, please take a look at the  information leaflet  that came with your medication or ask your doctor or pharmacist for advice.

Dosage of metoprolol

The exact dosage of metoprolol always depends on the underlying disease. Therefore, please consult your doctor about the exact dosage and consider the following information only as general guidelines. 

  • High blood pressure and coronary artery disease:  Take either 50 milligrams of metoprolol once or twice a day or 100 milligrams of metoprolol once a day. The dose can be increased up to 100 milligrams twice a day. 
  • Heart rhythm disturbances:  Take 100 milligrams of metoprolol once or twice a day. 
  • Heart attack (acute and long-term treatment):  Please discuss with your doctor how metoprolol should be taken during the acute treatment of a heart attack. After the acute therapy, take 100 milligrams twice a day. 
  • Migraine prophylaxis:  Take 100 milligrams of metoprolol once or twice a day. 

What to do if you overdose on metoprolol?

If you have taken too high a dose, you should immediately call a  doctor or an emergency doctor.

Depending on the dose, a sharp drop in blood pressure and a low heart rate or even cardiac arrest can occur. In addition, breathing difficulties, impaired consciousness, vomiting and spasms of the bronchial muscles can occur.

Discontinue metoprolol

In general, the dosage of metoprolol may only be changed after consultation with the doctor treating you. After prolonged treatment, the active ingredient should never be discontinued suddenly, otherwise dangerous side effects can occur: This can lead to a rapid rise in blood pressure or reduced blood flow to the heart muscle. This can worsen an existing  angina pectoris  or cause a heart attack.

Therefore, the dose should be slowly  reduced step by step  before the active ingredient can finally be discontinued. 

Metoprolol: contraindications 

Metoprolol should not be used if there is hypersensitivity to the active substance. In addition, the active ingredient must not be taken with certain heart problems, including

  • severe cardiac insufficiency that has not been adequately treated
  • a cardiogenic shock
  • a slow heartbeat (bradycardia)
  • conduction disorders

In addition, metoprolol must not be taken in a number of other diseases. This includes:

  • Lung diseases such as  bronchial asthma
  • a low blood pressure
  • untreated diseases of the adrenal medulla
  • hyperacidity of the blood or another   disturbance of the acid-base balance
  • Circulatory disorders such as Raynaud’s syndrome

Metoprolol may only be used in diabetics with fluctuating blood sugar levels, patients with hyperthyroidism, impaired kidney function, bronchial muscle spasms or psoriasis after a careful risk-benefit analysis by the treating doctor. The same applies to patients who are being treated with inhalation anesthetics or are undergoing desensitization. 

Danger in diabetes and impaired liver and kidney function

Diabetics should have their blood sugar levels checked regularly while taking the drug. Because the use of metoprolol can increase the  risk of hypoglycaemia  . This is because the effect of insulin or other antidiabetics can be prolonged or increased. In addition, warning signs of low blood sugar such as muscle tremors or tachycardia can be disguised. 

 Caution is also advised in patients with  liver or kidney dysfunction : In patients with liver dysfunction, the dosage may have to be reduced because the active ingredient is broken down more poorly. If the kidney function is reduced, regular monitoring of the kidneys is recommended. It is possible that kidney function may deteriorate as a result of taking the beta-blocker. 

Interactions with metoprolol

To avoid interactions, no other beta-blockers should be administered while taking metoprolol. It is also better to avoid the administration of other antiarrhythmic drugs – in particular calcium antagonists (both of the verapamil, diltiazem and nifedipine types).

Problems can also occur if you take the following at the same time:

  • trizyklischen Antidepressiva
  • Neuroleptika
  • Antihistaminika
  • ACE-Hemmern (zum Beispiel Ramipril)
  • Narkotika
  • Diuretika
  • Vasodilatatoren
  • Phenothiazinen
  • Barbituraten

Auch die Wirkstoffe Floctafenin, Sultoprid und Nitroglycerin sollten nicht gemeinsam mit Metoprolol eingenommen werden. Je nach Medikament kann es ansonsten zu einem starken Blutdruckabfall, einer Verringerung der Herzfrequenz oder Herzrhythmusstörungen kommen.

Wechselwirkungen können darüber hinaus auch mit Herzglykosiden sowie den Wirkstoffen Reserpin, Guanfacin, Guanethidin, alpha-Methyldopa und Clonidin auftreten. Als Wechselwirkungen sind ebenfalls ein Absinken der Herzfrequenz sowie Probleme bei der Reizüberleitung möglich. Bei gleichzeitiger Einnahme von MAO-Hemmern, Adrenalin oder Noradrenalin kann ein starker Anstieg des Blutdrucks ausgelöst werden. Cimetidin kann dagegen die Wirkung von Metoprolol verstärken.

Metoprolol in der Schwangerschaft

Ob durch die Einnahme von Metoprolol während der Schwangerschaft Risiken für das ungeborene Kind bestehen, ist bislang nicht genügend erforscht. Deswegen sollten Sie während der Schwangerschaft auf die Einnahme des Wirkstoffes verzichten oder diesen zumindest erst nach einer sorgfältigen Risiko-Nutzen-Analyse durch den behandelnden Arzt einnehmen.

Unter Umständen kann Metoprolol die Durchblutung der Plazenta verringern und dadurch Wachstumsstörungen beim ungeborenen Kind hervorrufen. Muss der Wirkstoff während der Schwangerschaft eingenommen werden, sollte er auf jeden Fall zwei bis drei Tage vor dem errechneten Geburtstermin abgesetzt werden, um schwere Nebenwirkungen für den Säugling zu vermeiden. Ist dies nicht möglich, muss das Kind zwei bis drei Tage nach der Geburt streng überwacht werden.

Metoprolol in der Stillzeit

Metoprolol sollte auch während der Stillzeit möglichst nicht eingenommen werden, da der Wirkstoff in die Muttermilch übergeht. Ist eine Einnahme zwingend notwendig, sollte abgestillt werden oder das Kind erst drei bis vier Stunden nach der Einnahme gestillt werden. Dann ist die Konzentration des Wirkstoffes bereits deutlich abgesunken.

In such a case, the infant should be regularly checked by a doctor for blockage of the beta-receptors. 

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