Beta-blockers,a futuristic-sounding name, is a group of medications that are widely used to treat heart-related diseases. According to the Malaysian Statistics on Medicines published in 2007, beta blockers were the most commonly prescribed high blood pressure medications. Although 14 years later we have better choices for high blood pressure such as angiotensin-converting enzyme inhibitors (ACEI, the drug name ends with “-pril”), beta-blockers still have its importance in other areas of medical treatment.
Recognise beta-blockers
Beta-blockers have names that end with “-prolol”. Examples are metoprolol, atenolol, bisoprolol and carvedilol.
Pharmaniaga Metoprolol tab 100 mg
Pharmaniaga Atenolol FC tab 100 mg
Pharmaniaga Atenolol FC tab 50 mg
Concor (Bisoprolol) FC tab 2.5 mg
Concor (Bisoprolol) FC tab 10 mg
Concor (Bisoprolol) FC tab 5 mg
Vacodil (Carvedilol) tab
Why are they called “beta-blockers”
The answer lies within how beta-blockers work. Even if you haven’t heard of beta-blockers before this, you definitely know what adrenaline is — a hormone that raises your blood pressure and heart rate when you’re under stressful conditions.
Beta-blockers work by blocking the “entrance door” where adrenaline would normally come out and exert its actions, known as the beta-adrenergic receptors. That’s why they’re called “beta-blockers”.
As a result of this blockade, your heart rate drops and your blood pressure is lower after using beta-blockers. Beta blockers also help open up your veins and arteries to improve blood flow.
Use of beta-blockers
As mentioned above, beta-blockers are commonly used in the following conditions:
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Chest pain (angina)
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Heart failure
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Heart attacks
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Irregular heart rhythm (arrhythmia)
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Heart palpitations and tremors in anxiety or hyperthyroidism
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Prevention of migraine (only two beta-blockers called propranolol and timolol are used for this purpose)
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Hypertension, but usually in combination with other blood pressure medications and only if other alternatives don’t work
The dose, frequency and administration time of beta-blockers may vary depending on the type and severity of the medical conditions.
Major side effects of beta-blockers
The blockage of beta-adrenergic receptors we mentioned above can be useful for treating certain medical conditions, but it may also bring unwanted side effects.
Slowing down of heart rate
The medical term for slowing of the heart rate is known as bradycardia. Slowing down of heart rate is a normal and expected response towards beta-blocker treatment. Therefore, its use is avoided in patients with heart block problems or who are also receiving other medications that also slow down heart rate, such as digoxin or certain calcium channel blockers.
Worsens breathing problems
Not all beta-blockers behave the same way. Propranolol, a beta-blocker with broader action, may restrict breathing in patients with breathing problems such as asthma. Whereas such issue is less common with other more specific-acting beta-blockers, such as metoprolol and bisoprolol. This is why when a person is starting a beta-blocker treatment, the doctor may spend a longer time to take proper medical history, so that the treatment does not bring about unwanted side effects like this.
Drop in blood sugar level
This is known as hypoglycemia. Because adrenaline promotes blood sugar production and utilisation, the use of beta-blockers may reduce such sugar metabolism and leads to reduction in blood sugar level. In addition, adrenaline also helps to alert you when you experience drop in blood sugar by making you sweat and anxious. Non-specific beta-blocker treatment such as propranolol may mask this effect, causing a person to have no knowledge of its own dangerously low blood sugar level. This is especially dangerous for individuals who are on insulin therapy for diabetes and beta-blocker at the same time, because extremely low blood sugar levels can be fatal. Fortunately, beta-blockers that are more specific in their action (such as carvedilol) are less likely to cause this issue.
Depression, fatigue and sexual dysfunction
Depression, fatigue and sexual dysfunction are commonly cited side effects of beta-blockers. While some smaller and poorer quality studies have concluded as such, the best available data on this issue come from a systematic review of randomized trials, which found no increased risk of depression with beta-blockers therapy, and only small increases in fatigue and sexual dysfunction. Interestingly, a small study suggested that the sexual dysfunction occurring with beta-blocker therapy is possibly related to knowledge about this as a side effect and the anxiety provoked, rather than as a direct consequence of the medication. If your doctor thinks that you need a beta-blocker therapy, you should not withhold from it for concerns of sexual dysfunction and fatigue.
Other side effects
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Increased level of potassium, known as hyperkalaemia — However, increase in potassium level caused by beta-blocker is rarely serious. This would only be a matter of concern if the patient also has other medications or diseases that raises the level of potassium in blood. Too much potassium in blood can affect how the heart works and even lead to cardiac arrest.
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Weight gain — Most of the weight gain occurred within the first few months of starting beta-blocker therapy. A systematic review of eight randomized trials of beta blockers versus placebo in hypertensive patients revealed a median increase in body weight in the beta blocker group of 1.2 kg only (range -0.4 to 3.5 kg).
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Increased blood lipid level — However this is not a general observation across all beta-blockers. Some beta-blockers (such as metoprolol) may raise the “bad cholesterol” modestly, while some don’t (e.g. carvedilol).
Takeaway
If you’re currently on a beta-blocker therapy, or know someone who does, here are things to remember:
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Always take your medication on time, according to the directions given by your doctor or pharmacist.
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Do not abruptly stop taking beta-blocker, as it may precipitate beta-blocker withdrawal, a condition that may worsen heart problems, even among those who don’t have heart problems to begin with! If your doctor wants to gradually reduce your beta-blocker dose, he or she would give you clear instructions on how to come down from your previous dose safely.
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Consult your doctor or pharmacist before taking other medications or supplements in addition to beta-blocker therapy. Beta-blockers may interact with other medications and supplements, thus leading to unwanted adverse effects.
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If you have concerns regarding the side effects of beta-blockers, do not stop taking them without consulting a healthcare professional first.
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References
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UpToDate - Major side effects of beta blockers
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Frishman, W., 2003. Beta-Adrenergic Blockers. Circulation, 107(18).
Cover image credit: Image by Steve Buissinne from Pixabay
