Synonyms in a broader sense
Metoprolol, Beloc
Introduction
Belok zok® is a drug that is used to treat cardiovascular diseases. It belongs to the ß-blocker (beta-receptor blocker) drug class and contains the drug metoprolol. The beta-receptors are divided into three subgroups.
ß1-receptors are found in the heart, where their activation causes the heart to beat faster (positively chronotropic) and with more force (positively inotropic). In addition, ß1-receptors are found in the kidney, where their activation leads to the release of the hormone renin. The result is a rise in blood pressure.
ß2-receptors are found in the muscles of the bronchi, uterus and blood vessels of the skeletal muscles. The activation of these receptors leads to an expansion. Finally, ß3-receptors are found in fatty tissue where, when activated, they cause its dissolution (lipolysis) and contribute to temperature regulation.
Beloc zok® acts mainly on the ß1-receptors in the heart and kidneys. Beloc zok® is available only on prescription and should not be discontinued abruptly after a longer therapy. Beloc zok® acts on the cardiovascular system by blocking the ß1 receptors located there.
At the heart, these receptors are found in the cells where the electrical activity of the heart action is generated and transmitted (excitation formation and conduction system). They are also found on the coronary vessels. A stimulation of the ß1-receptors normally causes an increase in the heart rate and an increased beating power.
By blocking these receptors, Belok zok® therefore causes a decrease in heart rate and power. The excitation is conducted more slowly. This also reduces the probability of an irregular heartbeat.
However, the blood pressure-lowering effect of Beloc zok® is less due to the blockage of the ß1-receptors in the heart. The blockage of the receptors in the kidney is the main reason for the blood pressure-lowering effect. This is because the hormone renin is not released.
Renin is normally released into the bloodstream by specialised cells (juxtaglomerular apparatus) in the kidney. This is followed by a cascade with the release and activation of numerous other substances, which ultimately have a blood pressure-increasing effect. By blocking the ß1-receptors in the kidney, the cascade is interrupted at an early stage. However, it should be kept in mind that the release of renin through ß1-receptor stimulation in the kidney is only one of three pathways. Thus, despite blockage of the β1 receptors, there is still a certain release of the hormone renin.
Pharmacokinetics
Beloc zok® (metoprolol) is usually taken orally as a tablet and absorbed through the intestinal mucosa. Since the blood supplying the intestine is first passed through the liver, the liver then directly eliminates about half of the active ingredient by absorbing and metabolising it. Due to this so-called first-pass effect, only about 50% of the originally supplied active ingredient is available to the organism.
After 1 – 2 hours the effective level in the blood is at its highest and after about 4 – 5 hours half of the active ingredient is broken down (elimination half-life). The breakdown of Belok zok® or metoprolol takes place via an enzyme (CYP2D6) in the liver. The products of the metabolic process in the liver enter the blood again and are then excreted via the kidneys and urine.
