Beta blockers

Beta blockers work by inhibiting the effects of the hormone adrenaline (also called epinephrine) in the body, particularly its stimulating effects on the heart.

As a result, these medications reduce heart rate and blood pressure, making the heart beat more slowly and with less force.

Specifically, beta blockers act by binding to beta-adrenergic receptors, thereby preventing adrenaline from activating them. These receptors are found in the myocardium (heart muscle) and the vascular system (blood vessels).

There are two main types of beta-adrenergic receptors:

• Beta-1 receptors: Primarily located in the heart and, to a lesser extent, in the kidneys. They regulate heart rate, contractility, and rhythm.
• Beta-2 receptors: Found mainly in the smooth muscles of the lungs, blood vessels, and uterus. They influence muscle relaxation and dilation of airways and blood vessels.

Beta blockers are used to treat a variety of medical conditions, including the following:

• Cardiovascular Disorders
  • Angina pectoris (used as antianginals).
  • Myocardial infarction or heart attack.
  • Heart arrhythmias (used as antiarrhythmics).
  • Heart failure.
  • High blood pressure (used as antihypertensives).
• Other disorders
  • Glaucoma.
  • Thyrotoxicosis (excessive thyroid hormone).
  • Anxiety disorders.
  • Benign essential tremor.
  • Migraine prevention.

Beta blockers can be classified into two main types:

• Selective Beta Blockers: Selective or cardioselective beta blockers primarily block beta-1 receptors, which regulate heart rate and rhythm. These medications are commonly used for cardiovascular conditions. Examples include: acebutolol, atenolol, betaxolol, bisoprolol, celiprolol, esmolol, nebivolol and metoprolol.
• Non-Selective Beta Blockers: Non-selective beta blockers block both beta-1 and beta-2 receptors, affecting the heart as well as other systems, such as the lungs and blood vessels. They are used to treat various conditions, including high blood pressure, arrhythmias, and migraines. Examples include: carteolol, nadolol, oxprenolol, timolol, labetalol, carvedilol, penbutolol, propranolol and sotalol. Sotalol is also used to treat arrhythmias and carvedilol is effective for treating heart failure. Timolol and propranolol are commonly prescribed for migraine prevention. Timolol (eye drops) is used for managing ocular hypertension and glaucoma. If a patient has conditions such as asthma, COPD, or hypoglycemia, selective beta blockers are preferred, as non-selective beta blockers can exacerbate these conditions.

Beta blockers can cause several side effects, including:

• Reduced exercise tolerance.
• Impotence (erectile dysfunction).
• May trigger or worsen asthma symptoms limiting their use in individuals with respiratory conditions.
• Fatigue and lethargy are also common and can affect daily activities.
• Some beta blockers may reduce levels of high-density lipoprotein (HDL), also known as "good" cholesterol.
• Bradycardia (slowed heart rate).
• Dry skin and eyes.

Beta blockers are widely used to treat various medical conditions. Below are examples of commonly prescribed beta blockers, along with their primary indications and potential side effects:

• Atenolol is indicated for the treatment of essential hypertension, angina pectoris, heart arrhythmias, and acute myocardial infarction. Common side effects include fatigue, gastrointestinal disturbances, and bradycardia.
• Bisoprolol is suitable for managing high blood pressure, angina pectoris, and heart failure. Side effects often include fatigue, dizziness, headache, gastrointestinal disturbances, and bradycardia.
• Carvedilol is prescribed for essential hypertension, long-term management of ischemic heart disease, and congestive heart failure. However, it can cause several side effects, including fatigue, nausea, diarrhea, vomiting, abdominal pain, weight gain, dizziness, headache, difficulty breathing (dyspnea), pain in the extremities, and bradycardia.
• Nebivolol is used to treat essential hypertension and chronic heart failure. Its potential adverse effects include fatigue, vertigo, headache, dyspnea (shortness of breath), constipation, nausea, or diarrhea.
• Metoprolol is commonly used for high blood pressure, angina pectoris, heart arrhythmias, and migraine prevention. Possible side effects include fatigue, dizziness, headache, nausea, and bradycardia.
• Propranolol is prescribed for essential arterial and renal hypertension, anxiety, migraine prevention, essential tremor, and heart arrhythmias. In some cases, it is also used to treat infantile hemangiomas (strawberry mark). Side effects include fatigue, bradycardia, sleep disturbances, and an increase in triglyceride levels.
• Timolol is primarily used to manage high intraocular pressure and glaucoma. Common side effects include blurred vision, eye pain, irritation, discomfort, and redness. Additionally, betaxolol is another beta blocker often used for glaucoma treatment.

Yes, beta blockers are often used in combination with other antihypertensive medications to effectively manage high blood pressure.

A common combination involves a beta blocker and a diuretic, particularly one from the thiazide group, such as hydrochlorothiazide or chlorthalidone. This pairing enhances blood pressure control by combining the diuretic's fluid-reducing effects with the beta blocker's ability to slow the heart rate and reduce cardiac output.

Beta blockers can also be prescribed alongside medications from the ACE inhibitor (ACEI) group, such as ramipril. This combination is effective because ACE inhibitors relax blood vessels and complement the action of beta blockers, providing a more comprehensive approach to managing hypertension.