Vademecum of beta-blockers

Proven content

Beta-blockers is a term known primarily to people suffering from hypertension, cardiac arrhythmias or coronary artery disease. It is worth knowing more about beta-blockers.

Beta-blockers, or beta-blockers, have been prescribed by doctors since the 60s because of their effectiveness and low cost. Over the years, the indications and contraindications to the use of these drugs have changed significantly, so it is worth checking when it is recommended to take them, and when it is better to use other preparations. A basic understanding of how beta-blockers work will also be useful.

Like a key to a lock

In order to understand the mechanism of action of these drugs, it is necessary to recall some information from biology lessons. The human nervous system is not only the brain responsible for our conscious actions, but also the autonomic nervous system (AUN) that coordinates actions independent of our will. The AUN strains the brain to control bodily functions such as maintaining proper blood pressure, breathing rate, and heart rate.

Nature has equipped the AUN with two opposing parts: an excitatory part called the adrenergic (or sympathetic, or sympathetic) system, and an inhibitory part, called the cholinergic (or parasympathetic, or parasympathetic) system.

The stimulating part has receptors (α1, α2 and α3 as well as ß1, ß2, ß3 and ß4), to which the molecule of the drug taken by us attaches, causing the inhibition of the adrenergic system (these are adrenergic drugs or otherwise α, ß-blockers) or its agitation (adrenergic drugs). We can relate it to the operation of the key-lock system, where the key that goes to the lock can open or close the door. It should be added, however, that the key (read the drug) made by the “right” specialist may match many doors (receptors) at the same time and that is why some drug molecules attach to, for example, both the ß1 and ß2 receptors, but there are also such which bind only to the ß1 receptor. Therefore, the action of beta-blockers is multidirectional and complex.

That’s all for the disease …

Beta-blockers are especially recommended when hypertension is associated with coronary artery disease or when the patient has had a heart attack, as they then help to control the coronary heart disease and reduce the risk of recurrent infarction.

Selective beta-blockers are also used in glaucoma and disorders of intraocular pressure of the eye, as they lower the pressure of the eye’s vitreous fluid (betaxolol).

They are also used in the treatment of hyperthyroidism and in the treatment of migraine (propranolol, metoprolol), and even in the treatment of such interesting diseases as stage anxiety (see the box below about particular groups of beta-blockers).

For the rest of my life?

Patients often ask if beta-blockers need to be taken for the rest of their lives or if they cannot stop taking them once their well-being has improved. The very cautious gradual increase of the dose at the beginning of therapy proves that this group of drugs cannot be treated indulgently. To end beta-blocker therapy, the dose should also be gradually reduced over a period of several days. The point is not to cause the pressure to suddenly increase and the heart to beat faster.

Although these drugs eliminate the symptoms of the disease, they do not eliminate its causes, therefore, after their discontinuation, the blockade of ß receptors is released and the mechanisms stabilizing the heart and blood pressure become unregulated, which may be life-threatening (in patients with angina, it is at risk of a heart attack or cardiac arrhythmia).

Not for everyone

There are also situations in which this group of drugs should not be introduced to therapy at all or dosed very carefully. It is necessary to observe the patient and monitor the results of his examinations.

Some drugs in this group adversely affect the metabolism of fats and sugars, and this causes an increase in cholesterol and triglycerides in the blood. It also increases the resistance of our body to insulin, and also hides and makes the symptoms of hypoglycemia, i.e. lowering blood glucose (sugar) levels, unnoticeable for the patient. Therefore, the use of nonselective beta-blockers (especially high doses) is avoided in patients with severe or recurrent hypoglycaemia. The use of beta-blockers should also be avoided in patients with psoriasis, as they may worsen its course.

Contraindications in this group of drugs are divided into two groups:

• Absolute – conditions such as: second and third degree atrioventricular block in patients without a pacemaker; sinus bradycardia (slow heart rate) less than 60 beats per minute; shock originating from the heart (cardiogenic); decompensated bronchial asthma, decompensated disorders of the peripheral circulation; Prinzmetal’s angina.

• Relative – conditions such as sick sinus syndrome, XNUMXst degree AV block, bronchial asthma, diabetes, depression.

Be careful

People taking medications are most concerned about the side effects of their action. What does it look like with beta blockers? The first is bad news – they have the most side effects of any antihypertensive drug, including an excessively slow heart rate. So if your heart rate is below 50 beats per minute, be sure to inform your doctor. But there is also good news – a slowing of the heart rate can be avoided by gradually increasing the dose of the drug taken from the beginning of therapy.

When you start using drugs from this group, also pay attention to their indirect effect on motor skills and driving. This is associated with the risk of lowering blood pressure which will not stabilize until dose adjustment. If you have diabetes or have cholesterol problems, your doctor should carefully monitor the effects of the prescribed beta-blocker. It is also worth adding that the patients themselves consider the feeling of weakness and reduced ability to exercise as the most bothersome symptoms when using these drugs. The most common undesirable side effects (several of which lead to treatment discontinuation) include:

• circulatory failure, atrioventricular block, persistent excessive pressure drop, cold hands and feet, exacerbation of peripheral arterial disease symptoms;

• depression, visual and memory disturbances, hallucinations, nightmares;

• nausea, vomiting, abdominal pain, diarrhea or constipation, concealing symptoms of hypoglycaemia (ie hypoglycaemia) in patients with type I diabetes, a decrease in HDL cholesterol, and an increase in plasma triglycerides;

• exacerbation of the course or induction of an attack of bronchial asthma;

• temporary impotence in some men.

Of course, not everyone will experience these problems. However, if you notice anything disturbing, see a doctor immediately.

Mutual relations

Everyone probably knows it, but in practice they somehow forget it. Drugs interact, and beta blockers, of course. That is why it is always worth reporting to the doctor the fact of using other drugs chronically, and when taking over-the-counter preparations, you also need to check the leaflet for interactions. Beta-blockers may interact with drugs such as:

• calcium antagonists (Isoptin, Staveran, Diltiazem retard, Diacordin) – risk of an excessive slowdown of the heart rate;

• non-steroidal anti-inflammatory drugs (Metindol) – weakening of the hypotensive effect occurs;

• aluminum hydroxide (in anti-acid drugs, such as Alugastrin) – they slow down the absorption of beta-blockers;

• certain drugs for diabetes (Euclamin, Euglucan).

It is also worth being careful with alcohol – it slows down the absorption of beta-blockers and intensifies their depressive effects.

Text: Rafał Jabłoński, MA in pharmacy

Source: Let’s live longer