Mode of action of Metroprolol

Metoprolol belongs to the group of beta-blockers. Drugs of this group block the so-called beta-adrenoreceptors. By blocking these receptors, the effect of the stress hormones adrenaline and noradrenaline is reduced or prevented.

The main effects of drugs such as Metohexal are therefore on heart rate and blood pressure. Beta-blockers can be divided into different groups. The subgroups of beta-receptors are decisive here, of which there are beta-1 and beta-2 receptors.

The various drugs/active ingredients therefore differ primarily in their binding to the respective receptors. If a drug binds approximately equally to both subtypes, it is called a non-selective beta-blocker. However, since these non-selective agents act on the entire body and therefore lead to a number of side effects, there are now also more selective drugs that block only one subtype or block it more intensively.

Metoprolol belongs to the group of selective beta1-receptor blockers. Since the beta1 receptors are found almost exclusively in the heart, these beta blockers are also called cardioselective. The active ingredient thus lowers the heart rate, the contractile force of the heart and the transmission of excitation to the heart.

Metabolization of Metroprolol

Metoprolol/Metohexal is almost completely absorbed in the gastrointestinal tract via the intestinal mucosa after oral administration. However, systemic availability is significantly lower because metoprolol is subject to a high first-pass effect. In this context, the first-pass effect means a rapid metabolism of the drug during its first passage through the liver.

Absorbed through the intestinal mucosa, metoprolol reaches venous blood vessels in the intestine. These open into the so-called portal vein, a large vessel that transports blood in the direction of the liver.Metoprolol is already partially metabolized there and therefore no longer enters the body’s circulation to exert its effect. The liver cells possess a number of different enzyme complexes, each of which can break down different drugs.

These enzymes belong to the large supergroup of the so-called cytochrome P450 enzymes. A subunit of this group is called CYP2D6, which is responsible for the degradation of metoprolol, among other things. Since this enzyme also breaks down other drugs, it is possible that if this enzyme is taken at the same time, it can lead to interactions that must always be considered. Metohexal is almost completely metabolized in the liver and then excreted. If the liver is damaged, leading to so-called cirrhosis of the liver, the metabolism can be impaired and therefore lead to increased drug levels in the blood.