Beta-blocking drugs

- as you can easily guess - they are active principles able to antagonize the β-type receptors for adrenaline and noradrenaline. Therefore, these drugs exert a sympatholytic action through the decrease of adrenergic and noradrenergic transmission.

Adrenaline and Noradrenaline receptors

There are three different types of β-adrenergic receptors:

β1, located at the cardiac, renal and ocular level (the activation of these receptors increases the work of the heart, stimulates the secretion of renin and the production of aqueous humor at the ocular level);
β2, located in the arteriolar, genito-urinary, gastrointestinal and bronchial smooth muscles (the activation of this receptor favors its relaxation); they are also found in the skeletal muscles, liver and mast cells. Furthermore, these receptors are also involved in the release of insulin.
β3, located mostly in the adipose tissue, at the level of which they stimulate lipolysis.

Beta-blockers of therapeutic interest are mainly those with selectivity for β1 receptors, although there are also non-specific beta-blocking drugs on the market that interact with both β1 and β2 receptors.

, such as hypertension and exertional angina.

In addition, some types of beta-blocking drugs are used in the treatment of cardiac arrhythmias, heart failure and secondary prevention of myocardial infarction; while still others are used in the treatment of glaucoma, thyrotoxicosis, somatic manifestations of anxiety, essential tremor and in the prophylactic treatment of migraine.

, nadolol, timolol and pindolol.

second generation β-blockers: these drugs are cardioselective; therefore, they preferentially interact with the β1 receptors located in the heart. However, it should be emphasized that this cardioselectivity is only relative, in fact, at high concentrations even this type of beta-blocker is able to interact with the β2 receptors.
However, thanks to their relative selectivity, these drugs - unlike non-selective beta-blockers - can also be used in individuals with diabetes and bronchospasm (such as asthma and COPD), since they do not interfere with β2 receptors involved in insulin release and bronchoconstriction. In any case, this category of patients still needs careful monitoring during the use of beta-blockers, even if cardioselective.
This group includes active ingredients such as metoprolol, atenolol, esmolol (characterized by a short half-life and used in emergencies), acebutolol and bisoprolol.

Third generation β-blockers with additional effects: carvedilol and labetalol belong to this group. These active principles, in addition to blocking the β1 receptors, also exert an "antagonistic action on the β2 receptors and on the α1 receptors present in the blood vessels. It is precisely the interaction with this last type of receptor that causes these principles active are also endowed with a "vasodilatory activity.

Third generation β-blockers with additional and selective β1 effects: the active ingredients belonging to this group show selectivity for β1 adrenergic receptors; moreover, they also possess other activities capable of assisting the antihypertensive action.
Among the active ingredients belonging to this group we find:

Celiprolol which is also endowed with agonist activity against β2 receptors (therefore it favors the relaxation of vascular smooth muscle);
Nebivolol, an active ingredient that is also able to stimulate the secretion of nitric oxide (NO) by the endothelium, thus inducing vasodilation.

Furthermore, some of the aforementioned active ingredients are grouped into a further group, that of beta-blocking drugs with intrinsic sympathomimetic activity (or ISA). Among these, we mention pindolol and acebutolol.
These molecules are not real antagonists of beta-adrenergic receptors, but are partial agonists which - once bound to the β-adrenergic receptor - partially stimulate it (thus preventing the binding of adrenaline or noradrenaline), up to to block it completely.
Generally, this type of drug produces less depression of heart function; for this reason, the use of these active ingredients is preferable in bradycardic patients.

contraction and heart rate. In addition to this, these active ingredients also affect renin secretion, inhibiting it. In doing so, beta-blocking drugs also interfere with the renin-angiotensin system, with a reduction in hydro-saline retention and consequently in blood volume and peripheral resistance.

choice and sensitivity of each individual towards the drug he intends to use.
However, some side effects are common to most beta blocker drugs. Among these, we remember:

Heart failure;
Bradycardia (may occur especially in the case of using beta-blockers without intrinsic sympathomimetic activity);
Acute hypotension;
Peripheral vasoconstriction;
Bronchoconstriction;
Hypoglycemia;
Gastrointestinal disturbances, such as nausea, vomiting and diarrhea;
Dizziness
Insomnia;
Depression;
Nightmares and hallucinations;
Visual disturbances;
Muscle cramps
Skin rashes;
Purple;
Alopecia.

Finally, it should be remembered that - to avoid a "hyperactivity of the β receptors which can degenerate into dangerous hypertensive crises - therapy with beta-blockers must" be discontinued gradually.

, due to the possible side effects that could occur. In any case, before taking any type of drug, pregnant women and mothers who are breastfeeding should always seek the advice of the doctor, who will carry out a "careful evaluation of the relationship between the expected benefits for the mother and the potential risks to the fetus or baby.

(COPD) or other conditions associated with bronchoconstriction;

In bradycardic patients;

In patients with diabetes and treated with insulin;

In patients with hypoglycemic syndromes;

In patients with liver function disorders.

However, it should be remembered that in patients suffering from pathologies associated with bronchospasm and in bradycardic patients, cardioselective beta-blocking drugs and ISA beta-blocking drugs, respectively, can be administered, provided that the use of these same active ingredients is carried out with great caution and under the close supervision of the doctor.