Synonyms in a broader sense
- Metoprolol
- Beloc
- Beta blocker
Side effects
Beta-blockers such as Beloc zok® can lead to a too slow heartbeat (bradycardia, negative chronotropic). They can also slow down the transfer of excitation (negatively dromotropic, AV block) as well as reduce the strength of the beat (negatively inotropic). Beloc zok® can trigger an asthma attack by blocking other ß-receptors, especially when asthma is already present.
The ß2-receptors in the liver can also be blocked. This can be particularly important in diabetics, because the blockage of the receptors inhibits the dissolution of the sugar storage glycogen in the liver (glycogenolysis). Diabetics who are treated with insulin or sulfonylureas therefore have an increased risk of hypoglycemia.
This risk can be further increased by using beta blockers to suppress important warnings of hypoglycaemia. Warnings of hypoglycaemia include rapid heartbeat (tachycardia), tremors and sweating. Other undesirable effects are fatigue and even depressive moods (rare). Beta-blockers such as Beloc zok® can also influence the blood circulation, which can manifest itself in an aggravation of a circulatory disorder of the legs (pAVK) or – more likely in men – in potency disorders.
Rebound effect
Beta blockers such as Beloc zok® must not be discontinued abruptly after prolonged use. There is a risk of a rebound effect. This is manifested by a higher blood pressure and a faster heartbeat (tachycardia) and can even lead to symptoms of a narrow heart (angina pectoris).
The cause of the rebound effect is a physiologically upregulated receptor density at the cells due to the long-lasting blockade of the ß-receptors by the body. The body also adjusts to an increased release of so-called catecholamines. Catecholamines are the physiological activator of the ß-receptors.
The body therefore tries to control against this therapy under the beta blockers. This process is physiological. So there are more receptors and more catecholamines.
This becomes critical when beta-blockers (Belok zok) are abruptly stopped and suddenly all or more receptors are activated again – with a simultaneously increased level of activators. This leads to an exuberant reaction. Therefore, beta blockers like Beloc zok® have to be phased out slowly so that the body can get used to it again, so to speak. The receptor density and the amount of catecholamines produced and released are then slowly reduced.
Interactions
Interactions of Belok zok can occur above all when the drug metoprolol is administered i.v. (intravenously, injected into a vein or as an infusion) and the affected person is already being treated with medication against cardiac arrhythmia (antiarrhythmics). The same applies to the intravenous administration of medication against irregular heartbeat (antiarrhythmics) if the person concerned is already receiving therapy with Beloc zok®. Interactions of beta blockers with antiarrhythmic drugs (e.g. calcium antagonists of the diltiazem or verapamil type) can lead to a very slow heartbeat (bradycardia).