Beta blockers also written β-blockers, are a class of medications that are particularly used to manage abnormal heart rhythms, and to protect the heart from a second heart attack (myocardial infarction) after a first heart attack (secondary prevention). They are also widely used to treat high blood pressure (hypertension), although they are no longer the first choice for initial treatment of most patients
Beta blockers inhibit the chronotropic, inotropic, and vasoconstrictor responses to the catecholamines, epinephrine, and norepinephrine. Most beta blockers have half-lives of over 6 hours. The shortest actings are pindolol (3 to 4 hours) and propranolol (3 to 5 hours). Most of the included beta blockers are metabolized in combination by the liver and kidneys, with the exception of atenolol, which is metabolized primarily by the kidneys while the liver has little to no involvement.
Classifications/Types of Beta-blockers
α1-receptor antagonism
Some beta blockers (e.g., labetalol and carvedilol) exhibit mixed antagonism of both β- and α1-adrenergic receptors, which provides additional arteriolar vasodilating action.
Nonselective agents
Nonselective beta-blockers display both β1 and β2 antagonism.
- Propranolol
- Bucindolol (has additional α1-blocking activity)
- Carteolol
- Carvedilol (has additional α1-blocking activity)
- Labetalol (has additional α1-blocking activity)
- Nadolol
- Oxprenolol (has intrinsic sympathomimetic activity)
- Penbutolol (has intrinsic sympathomimetic activity)
- Pindolol (has intrinsic sympathomimetic activity)
- Sotalol (not considered a “typical beta blocker”)
- Timolol
β1-selective agents
β1-selective beta blockers are also known as cardioselective beta blockers.
- Acebutolol (has intrinsic sympathomimetic activity, ISA)
- Atenolol
- Betaxolol
- Bisoprolol
- Celiprolol (has intrinsic sympathomimetic activity)
- Metoprolol
- Nebivolol
- Esmolol
β2-selective agents
- Butaxamine
Classification of overall
| β, non-selective |
|
|---|---|
| β1-selective |
|
| β2-selective |
|
| α1– + β-selective |
|
Pharmacological differences of Beta-blockers
Agents with intrinsic sympathomimetic action (ISA)
- Acebutolol, pindolol, labetalol, mepindolol, oxprenolol, celiprolol, penbutolol
Agents organized by lipid solubility (lipophilicity)
- High lipophilicity: propranolol, labetalol
- Intermediate lipophilicity: metoprolol, bisoprolol, carvedilol, acebutolol, timolol, pindolol
- Low lipophilicity (also known as hydrophilic beta-blockers): atenolol, nadolol, and sotalol
Agents with membrane stabilizing the effect
- Carvedilol, propranolol > oxprenolol > labetalol, metoprolol, timolol
Indication differences of Beta-blockers
Agents specifically labeled for cardiac arrhythmia
- Esmolol, sotalol, landiolol (Japan)
Agents specifically labeled for congestive heart failure
- Carvedilol, sustained-release metoprolol
Agents specifically labeled for glaucoma
- Betaxolol, carteolol, levobunolol, timolol, metipranolol
Agents specifically labeled for myocardial infarction
- Atenolol, metoprolol (immediate release), propranolol (immediate release), timolol, carvedilol (after left ventricular dysfunction)
Agents specifically labeled for migraine prophylaxis
- Timolol, propranolol
Propranolol is the only agent indicated for the control of tremor, portal hypertension, and esophageal variceal bleeding, and used in conjunction with α-blocker therapy in phaeochromocytoma.
Mechanism of action of Beta-blockers
Beta-blockers compete with sympathomimetic neurotransmitters such as catecholamines for binding at beta(1)-adrenergic receptors in the heart, inhibiting sympathetic stimulation. This results in a reduction in resting heart rate, cardiac output, systolic and diastolic blood pressure, and reflex orthostatic hypotension.
Beta blockers are classified as a non-cardioselective sympatholytic beta blocker that crosses the blood-brain barrier. It is lipid soluble and also has sodium channel blocking effects. Beta blockers are a non-selective beta blocker; that is, it blocks the action of epinephrine (adrenaline) and norepinephrine (noradrenaline) at both β1– and β2-adrenergic receptors. It has little intrinsic sympathomimetic activity but has strong membrane stabilizing activity (only at high blood concentrations, e.g. overdose). Beta blockers are able to cross the blood-brain barrier and exert effects in the central nervous system in addition to its peripheral activity.
In addition to blockade of adrenergic receptors, beta blockers have very weak inhibitory effects on the norepinephrine transporter and/or weakly stimulates norepinephrine release (i.e., the concentration of norepinephrine is increased in the synapse). Since beta blockers blocks β-adrenoceptors, the increase in synaptic norepinephrine only results in α-adrenoceptor activation, with the α1-adrenoceptor being particularly important for effects observed in animal models. Therefore, it can be looked upon as a weak indirect α1-adrenoceptor agonist in addition to the potent β-adrenoceptor antagonist. In addition to its effects on the adrenergic system, there is evidence that indicates that Beta-blockers may act as a weak antagonist of certain serotonin receptors, namely the 5-HT1A, 5-HT1B, and 5-HT2Breceptors. The latter may be involved in the effectiveness of beta-blockers in the treatment of a migraine at high doses
Indication /Uses of Beta Blockers
Indications for beta blockers include
- Angina pectoris(contraindicated for Prinzmetal’s angina)
- Atrial fibrillation
- Cardiac arrhythmia
- Congestive heart failure
- Essential tremor
- Glaucoma (As eye drops, they decrease intraocular pressure by lowering aqueous humor secretion.
- Hypertension, although they are generally not preferred as an initial treatment.
- Migraine prophylaxis
- Mitral valve prolapse
- Myocardial infarction
- Phaeochromocytoma, in conjunction with α-blocker
- Postural orthostatic tachycardia syndrome
- Symptomatic control (tachycardia, tremor) in anxiety and hyperthyroidism
- Theophylline overdose
Beta blockers have also been used for:
- Acute aortic dissection
- Hypertrophic obstructive cardiomyopathy
- Long QT syndrome
- Marfan syndrome (treatment with propranolol slows progression of aortic dilation and its complications)
- Prevention of variceal bleeding in portal hypertension
- Possible mitigation of hyperhidrosis
- Social and other anxiety disorders
- Controversially, for reduction of perioperative mortality
Contra-Indications of Beta Blockers
- Diabetes
- Low amount of magnesium in the blood
- Complete heart block
- Second-degree atrioventricular heart block
- Very rapid heartbeat – torsades de pointes
- Sick sinus syndrome
- Sinus bradycardia
- Prolonged QT interval on EKG
- Suddenly serious symptoms of heart failure
- Abnormal EKG with QT changes from Birth
- Abnormally low blood pressure
- Asthma
- Bronchospasm
- Blood Circulation Failure due to Serious Heart Condition
- Pregnancy
- Moderate to severe kidney impairment
- Anaphylactic Shock due to Allergy Shots
Allergies to
- Beta-Blockers (Beta-Adrenergic Blocking Agents)
Side Effects
The most common
- Blurred vision
- pain or swelling in one or both legs;
- migraine headache;
- pale skin, feeling light-headed or short of breath, rapid heart rate, trouble concentrating; or
- Chest pain or discomfort
- headache
- Blurred vision or other vision problems
- Fever, chills, or sore throat
- Shortness of breath
- Slow or irregular heartbeat
- Dry mouth /cough
- muscle trembling, jerking, or stiffness
- anxiety
- changes in vision, including blurred vision
- dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
- stomach pain or cramping
- diarrhea
- stomach pain;
- back pain, joint or muscle pain.
- problems with your vision (including color vision);
- sudden chest pain or trouble breathing;
- pain or swelling in one or both legs;
- migraine headache;
- pale skin, feeling light-headed or short of breath, rapid heart rate, trouble concentrating;
More common
- Abdominal or stomach pain, discomfort, or tenderness
- chills or fever
- difficulty with moving
- a headache, severe and throbbing
- joint or back pain
- muscle aching or cramping
- muscle pains or stiffness
- chest pressure or squeezing pain in the chest
- discomfort in arms, shoulders, neck or upper back
- excessive sweating
- feeling of heaviness, pain, warmth and/or swelling in a leg or in the pelvis
- sudden tingling or coldness in an arm or leg
- sudden slow or difficult speech
- sudden drowsiness or need to sleep
- fast breathing
- sharp pain when taking a deep breath
- fast or slow heartbeat
- coughing up blood
- rust colored urine
- decreased amount of urine
Rare
- Anxiety
- change in vision
- chest pain or tightness
- confusion
- a cough
- Agitation
- arm, back, or jaw pain
- blurred vision
- chest pain or discomfort
- convulsions
- extra heartbeats
- fainting
- hallucinations
- a headache
- irritability
- lightheadedness
- mood or mental changes
- muscle pain or cramps
- muscle spasm or jerking of all extremities
- nervousness
Drug Interactions of Beta-blockers
Beta blockers may interact with the following drug, supplyments, & may change the efficacy of the drug
- alpha-1 blockers (e.g., doxazosin, prazosin, tamsulosin)
- alpha-2 blockers (e.g., clonidine, dexmedetomidine, methyldopa)
- angiotensin-converting enzyme inhibitors (ACEIs; e.g., captopril, ramipril)
- angiotensin II receptor blockers (i.e., irbesartan, losartan, valsartan)
- antipsychoticss (e.g., clozapine, olanzapine, quetiapine, risperidone)
- atorvastatin
- azole antifungals (e.g., itraconazole, ketoconazole, posaconazole)
- barbiturates (e.g., phenobarbital)
- benzodiazepines (e.g., alprazolam, diazepam, lorazepam)
- beta-agonists (e.g., formoterol, salbutamol, salmeterol)
- calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil)
- carbamazepine
- cyclosporine
- dexamethasone
- diuretics (water pills; e.g., furosemide, hydrochlorothiazide)
- duloxetine
- lapatinib
- levodopa
- lidocaine
- MAO inhibitors (e.g., phenelzine, moclobemide, selegiline)
- macrolide antibiotics (e.g., azithromycin, clarithromycin, erythromycin)
- nilotinib
- nonsteroidal anti-inflammatory drugs (NSAIDs; e.g., ibuprofen, naproxen)
- other beta-blockers (e.g., atenolol, metoprolol, propranolol)
- pentoxifylline
- phosphodiesterase-5-inhibitors (e.g., sildenafil, tadalafil)
- sulfonylureas (e.g., gliclazide, glyburide, tolbutamide)
- sunitinib
- theophyllines (e.g., aminophylline, oxtriphylline, theophylline)
References
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