Introduction
Beta blockers are used for various heart diseases and high blood pressure. In addition to their effect on the heart and vessels, they can also influence other body functions or organs. The prescription of a beta blocker must therefore be carried out by a doctor who knows the correct dosage and the mechanism of action of the preparations and can therefore select the appropriate medication.
Mode of action
There are numerous docking sites in the body that are sensitive to certain messenger substances and hormones. If a messenger substance docks at this station, a physiological reaction is set in motion. In addition to the alpha-receptors, there are also so-called beta-receptors.
They are located at very different organ systems of our body. They are mainly found at the heart. But these receptors can also be found in the bronchial tubes, the uterus, in fatty tissue and in the blood vessels.
The physiological reason is that the messenger substance intended for this receptor is adrenaline. This is a stress hormone that is released and must act when the body is in a stress or emergency situation and must perform better than usual. An increase in blood pressure as well as an increase in heart rate (pulse rate increase) has a performance-enhancing effect.
In emergency situations, the muscle needs more blood per minute due to the physical load, which can only be ensured by increasing blood pressure and heart rate. In addition to an increase in blood flow, the body’s oxygen consumption is also increased. For this reason it is necessary that the lungs can also absorb more oxygen per minute.
To ensure this, beta-receptors are also located in the bronchial tubes. When adrenaline docks on these receptors, the bronchi dilate and the lungs can take in more oxygen. In addition to the heart muscle and lungs, beta-type receptors are also located in the blood vessels.
When adrenaline docks on, the lumen of the vascular system changes, which in turn has a circulation-promoting effect. Since beta receptors are also found in the uterus, adrenaline binding to these receptors inhibits contractions. This enables the body to accelerate or stop the birth process depending on the release of the various messenger substances.
The outflow of ocular fluid and thus the intraocular pressure can also be regulated by adrenaline and by corresponding receptors in the area of the eye. These receptors are also located on the smooth vascular muscles. If adrenalin binds to them, especially in the area of the intestinal muscles, digestive processes are reduced.
The background to this is that in stressful situations there is usually no need to take in food, so no digestive processes have to take place. The processes of normal metabolism now also offer the possibility of drug intervention. The placement of the beta receptors and the corresponding effect of adrenaline is used to block the receptors with drugs to achieve an opposite reaction.
By the so-called beta-receptor blockers, which represent a separate group of drugs, one achieves that these, after absorption, are placed on the corresponding receptors in the body and block them. Incoming adrenaline can no longer dock and therefore cannot have a physiological effect. In the heart this means that the heart rate is reduced.
Blood pressure is also reduced, although adrenaline is released in sufficient quantities. The eye pressure is lowered and the intestinal muscles are prevented to a small extent from reducing digestive processes. During pregnancy, beta blockers would ensure that the contractions are intensified and at the bronchial tubes, beta blockers prevent the lungs from dilating (see: Beta blockers during pregnancy).
As a result, asthmatics should not be given beta blockers as this could promote shortness of breath. Beta blockers should be administered slowly. If the desired effect is achieved, the dose should be left in the appropriate range.
It is important that sudden cessation should not be performed as the body has made its receptors more “sensitive” at the time of the blockade. This means that in the absence of the blockade, discontinuing the drug would result in a much stronger effect of the adrenaline. This would result in palpitations (tachycardia) or high blood pressure and could be dangerous.
Due to the large number of beta receptors in different organ systems, the biggest disadvantage of beta blockers is the relatively rough adjustment possibility. Thus one can roughly say that a beta blocker blocks all receptors and also leads to corresponding, even if unintended, effects. Today, there are also selective beta blockers that mainly affect receptors of one organ system, but one can never completely rule out that receptors of other organs are also affected.
The most common side effects of beta blockers are fatigue, fatigue, depression, headaches and impotence. Coughing and shortness of breath can also occur, but are more common when lung disease is prescribed. Our heart is controlled by the so-called autonomic nervous system.
There is the activating part, the so-called sympathetic nervous system and the damping part, the parasympathetic nervous system. The sympathetic nervous system acts on the heart via the stress hormones adrenaline and noradrenaline, which are released during physical activity, for example, and can thus increase heart rate, power and blood pressure. However, if there is a heart disease, such as cardiac insufficiency, rhythm disturbances or high blood pressure, it can be helpful to reduce this increase in heart performance so that the heart can better supply itself and work more economically.
This is where the beta-blockers come in, by blocking the docking sites, the so-called beta-adrenoreceptors, of the stress hormones and thus preventing them from having their effect. As a result, the heart beats more slowly, i.e. the heart rate is lowered. On the one hand, this ensures that the heart can now be better supplied with oxygen.
This can only happen if the heart relaxes and fills up again after the blood has been expelled. During this time oxygen reaches the heart muscles via the coronary arteries. When the heartbeat slows down, this phase, known as diastole, lasts longer and the oxygen supply to the heart increases.
In patients suffering from cardiac arrhythmia, the slower heartbeat can also help to promote the heart’s natural conduction of excitation. On the other hand, the heart now consumes less oxygen because the heart’s performance has been reduced. Doctors say that the heart works more economically, i.e. more efficiently.
This is particularly helpful for patients with cardiac insufficiency or recurrent chest pain (angina pectoris). Finally, beta blockers lower blood pressure. This not only relieves the heart, as it no longer has to pump against increased resistance, but also has a positive effect on our entire body, as increased blood pressure is known to be a risk factor for many diseases such as arteriosclerosis.
The side effects of beta blockers on mental health have been discussed for some time. The study situation is contradictory on this topic and the medical specialists seem to disagree. It is said that patients who take beta blockers have an increased risk of developing depression.
This is in contrast to studies that have formed two groups of patients, where only one group received the beta-blocker while the other group received a tablet without an active substance (placebo). Here it was shown that there was no clear difference between the two test groups and in this case there were even fewer patients suffering from depression in the beta-blocker group than in the comparison group. Accordingly, the effect of beta-blockers on the psyche has not been conclusively clarified.
