What are beta blockers?
Beta blockers are widely used prescription drugs that reduce strain on the heart.
They do this by preventing (blocking) the hormones epinephrine (adrenaline) and norepinephrine from binding to the sympathetic nervous system’s β1, β2, and β3 beta receptors located in the heart, kidneys, and lungs, as well as the liver, GI tract, womb, vascular muscle, skeletal muscle, and fat cells.
Sometimes called beta antagonists or beta-adrenergic antagonists, beta blockers slow the heart rate (heartbeat speed), dilate blood vessels, and lower blood pressure, reducing symptoms and damage in those who might benefit from taking them.
What do beta-blockers treat?
They are used in the treatment of various medical conditions, including angina pectoris (chest pain or pressure), heart failure, and atrial fibrillation (irregular heart beat). They also treat hypertension (high blood pressure), myocardial infarctions (heart attacks), and mitral valve prolapse.
Less commonly, they are used for treating migraines, anxiety, tremor, thyrotoxicosis (overactive thyroid), and glaucoma (eye disorders), as well as fibromyalgia, Marfan syndrome, cardiomyopathy, and aortic dissection. Beta blockers before/after heart surgery may prevent cardiac arrhythmias.
What types of beta blockers are available?
There are several types of beta-blockers available. They have different characteristics but differ mainly by which beta receptors they block. Which one you are prescribed depends upon your specific condition and circumstances. Here’s a list of beta blockers that are commonly used…
Selective blockers (block beta-1 receptors – heart and kidneys):
- Celiprolol (also a β2 partial agonist and α2 blocker)
Selective blockers (block beta-2 receptors – lungs, liver, gastrointestinal tract, womb, vascular muscle, and skeletal muscle):
Non-selective blockers (block beta-1 and beta-2 receptors):
- Carvedilol (also an alpha blocker – α1)
- Labetalol (also an alpha blocker – α1)
Are there any adverse beta-blocker side effects?
The drugs are generally well tolerated, but they can cause nausea, fatigue, and stomach cramps in some patients. They can also cause diarrhea, dyspnea (shortness of breath), bronchospasms, bradycardia (slow heart rate), hypotension (low blood pressure), and cold extremities.
Less common effects include headaches, dizziness, and insomnia, nightmares, hallucinations, blurred vision, alopecia (hair loss), sexual dysfunction, depression, hypoglycemia (low blood sugar), hyperglycemia, erectile dysfunction, heart block, and heart failure. The use of beta-blockers can exacerbate Raynaud’s syndrome and mask hypoglycemia symptoms in diabetics.
Are there any contraindications with beta blockers?
Beta-blocking drugs are contraindicated in some people, particularly those with 2nd or 3rd degree heart block, severe peripheral arterial disease, and progressive unstable heart failure.
Patients with a history of asthma, bronchospasms, kidney disease, cocaine use, and cocaine-induced tachycardia (fast heart rate) should not take beta blockers. The drugs should be used with caution by patients with diabetes, myasthenia gravis, and bradycardia, hypotension, hypertension, metabolic acidosis (high blood acid levels), and Prinzmetal’s angina.
Beta blockers should be avoided by pregnant and breastfeeding women, although they may be prescribed in certain cases.
Are there any beta blocker drug interactions?
Beta antagonists can interact with many medications, including digoxin (used in the treatment of heart failure and arrhythmias), clonidine (treats hypertension and migraines), diltiazem (for angina and hypertension), mefloquine (for malaria), and nifedipine (for angina).
They may also interact with verapamil (a calcium channel blocker that treats hypertension, angina, and arrhythmias), nisoldipine (used for treating high blood pressure), antipsychotics (for bipolar disorder and schizophrenia), antihypertensives (high blood pressure control), anti-arrhythmics (irregular heartbeats control), and barbiturates (central nervous system depressants).
What else should you know about these drugs?
Most beta-blocking drugs are taken once daily only, with the exception of certain blockers that are prescribed for women during pregnancy. These can be taken up to three times a day.
Never stop taking beta blockers (aka beta-adrenoreceptor antagonists and beta adrenergic receptor antagonists) suddenly, as doing so can intensify your symptoms and worsen your condition. Always seek advice from a medical professional first, who can show you how to wean off the drug.
Your pharmacist should have an up-to-date list of beta-blocker contraindications and interactions.
What if you miss a dose or overdose on beta blockers?
If you forget to take a dose, take the missed dose as soon as you remember. Skip the missed dose if your next scheduled dose is less than eight hours away, but be sure to take that next dose.
If you are unsure about what to do about your dose, check the information leaflet that comes with your medication (inside the box), and/or call your doctor or pharmacist asap.
If you accidentally or intentionally overdose on beta blockers (ensure that your children never have access to your medication), seek immediate medical attention. Call your local emergency number or poison control center. Even a single extra dose can be dangerous.