Beta-blockers: Uses, Differences, Side Effects, Interactions and Examples

Also known as beta-adrenergic blocking agents, they are a class of drugs that act by blocking the neurotransmitters norepinephrine and andepinephrine.

There are three known types of beta receptors, known as beta1 (β1), beta2 (β2) and beta3 (β3).

  • Β 1 -adrenergic receptors are commonly found in the heart and kidneys.
  • The β2-adrenergic receptors are located mainly in the lungs, the gastrointestinal tract, the liver, the uterus, vascular smooth muscle and skeletal muscle.
  • The β3-adrenergic receptors are found in fat cells.

When neurotransmitters are prevented from binding to the receptors, in turn, the effects of adrenaline ( epinephrine ) are blocked .

This action allows the heart to relax and release more slowly, thus reducing the amount of blood the heart must pump.

Over time, this action improves the heart’s pumping mechanism .

For what conditions are beta-blockers used?

Betablocks are used to handle a variety of conditions. They include, but are not limited to:

  • Cardiac arrhythmia.
  • Heart failure.
  • High risk of coronary artery disease.
  • Diabetes.
  • Posterior cardiac attack (myocardial infarction).
  • Angina of chest due to coronary atherosclerosis.
  • Hypertension (high blood pressure).

In the treatment of hypertension, it can be used alone or concomitantly with other antihypertensive agents, particularly thiazide diuretics.

Off-label uses of beta blockers include, among others:

Are there any differences between beta blockers?

Beta-blockers differ according to blocked receivers.

First-generation beta-blockers are known as:

  • Propranolol (Inderal, InnoPran).
  • Nadolol (Corgard).
  • Timolol maleate (Blocadren).
  • Penbutolol sulphate (Levatol).
  • Sotalol hydrochloride (Betapace).
  • Pindolol (Visken).

They are non-selective in nature, which means they block the beta1 (β1) and beta2 (β2) receptors and subsequently affect the heart, kidneys, lungs, gastrointestinal tract, liver, uterus, vascular smooth muscle and skeletal muscle.

As an effect, they could reduce cardiac output, reduce renal production among other actions.

Second-generation beta-blockers are known as:

  • Metoprolol (Lopressor, Toprol XL).
  • Acebutolol hydrochloride (Sectral).
  • Bisoprolol fumarate (Zebeta).
  • Esmolol hydrochloride (Brevibloc).
  • Betaxolol hydrochloride (Kerlone).
  • Acebutolol hydrochloride (Sectral).

They are selective, since they block only β1 receptors and, as such, will mainly affect the heart and cause a reduced cardiac output.

Beta-blockers such as pindolol (Visken), penbutolol sulfate (Levatol) and acebutolol hydrochloride (Sectral) differ from other beta-blockers in that they have intrinsic sympathomimetic activity (ASI).

This means that they mimic the effects of epinephrine and norepinephrine and can cause an increase in blood pressure and heart rate.

ASIs have less effect in reducing cardiac output at rest and resting heart rate, compared to drugs that do not have ASI.

Beta-blockers such as propranolol (Inderal, InnoPran), acebutolol hydrochloride (Sectral) and betaxolol hydrochloride (Kerlone) have a membrane action similar to quinidine or anesthetic, which affects the potential for cardiac action (electrical impulses in the heart causing contractions).

Beta-blockers such as labetalol hydrochloride (Trandate, Normodyne) and carvedilol (Coreg) may have both β1 and α1 adrenergic receptors. The blocking of α1-adrenergic receptors in addition to the β-blocker decreases blood pressure, which provides an additional vasodilatory action of the arteries.

What are the side effects of Beta-blockers?

Beta-blockers are generally well tolerated and most adverse events are mild.

Beta-blockers can cause diarrhea, stomach cramps, nausea, and vomiting.

Rashes, blurred vision, muscle cramps and fatigue have also been reported.

Beta-blockers can cause hypoglycemia or hyperglycemia and mask the symptoms of hypoglycaemia in diabetic patients.

Effects on the heart and circulatory system include bradycardia (slow heart rate), hypotension (low blood pressure), heart failure, or heart block in patients with heart problems, cold extremities due to reduced circulation.

Abstinence from beta-blockers can worsen angina (chest pain) and cause heart attacks or sudden death.

Effects on the central nervous system include headache, depression, confusion, dizziness, nightmares and hallucinations. Beta-blockers can cause breathing difficulties in asthmatics.

Sexual dysfunction can also occur.

What are the drug interactions?

The following medications cause an increase in plasma blood levels:
  • Pindolol (Visken) / Propranolol (Inderal, InnoPran) should not be taken with phenothiazines thioridazine and chlorpromazine (Thorazine). Due to the fact that increased levels of thioridazine could increase the risk of life-threatening cardiac arrhythmias, thioridazine is contraindicated in patients receiving pindolol and propranolol.
The following medications cause increases in blood pressure when taken with Clonidine:
  • Acebutolol hydrochloride (Sectral).
  • Atenolol (Tenormin).
  • Betaxolol hydrochloride (Kerlone).
  • Carteolol Hydrochloride (Cartrol).
  • Esmolol hydrochloride (Brevibloc).
  • Metoprolol (Lopressor).
  • Nadolol (Corgard).
  • Penbutolol sulphate (Levatol).
  • Pindolol (Visken).
  • Propranolol (Inderal, InnoPran).
  • Timolol maleate (Blocadren).
The following medications may affect the lung organs and cause bronchospasm when taken with beta-agonists:
  • Carteolol Hydrochloride (Cartrol).
  • Nadolol (Corgard).
  • Penbutolol sulphate (Levatol).
  • Pindolol (Visken).
  • Propranolol (Inderal, InnoPran).
  • Timolol maleate (Blocadren).
  • Sotalol hydrochloride (Betapace).
The following medications cause a reduction in blood plasma when taken with barbiturates:
  • Metoprolol (Lopressor, Toprol XL).
  • Propranolol (Inderal, InnoPran).

What are some examples of Betablocks?

Beta-adrenergic blocking agents:

  • Acebutolol hydrochloride e (Sectral).
  • Atenolol (Tenormin).
  • Betaxolol hidrocloruro (Kerlone).
  • Bisoprolol fumarato (Zebeta).
  • Carteolol Hydrochloride (Cartrol).
  • Esmolol hidrocloruro (Brevibloc).
  • Metoprolol (Lopressor, Toprol XL).
  • Penbutolol sulfato (Levatol).
  • Nadolol ( Corgard).
  • Nebivolol (Bystolic).
  • Pindolol (Visken).
  • Propranolol (Inderal, InnoPran).
  • Timolol maleate (Blocadren).
  • Sotalol hydrochloride (Betapace).
  • Carvedilol (Coreg).
  • Labetalol hydrochloride (Trandate, Normodyne ).