A Comprehensive Analysis of Precautions for Hypertension Medication: Beta-blockers

Which hypertensive patients are NOT suitable for beta-blockers?

This product is not suitable for the following hypertensive patients:

① Patients with acute heart failure.

② Patients with bronchial asthma.

③ Patients with a pre-existing slow heart rate (below 55 beats/min).

④ Patients with severe atrioventricular block.

What precautions should be taken when using beta-blockers?

The following precautions should be taken when using beta-blockers:

① Individual responses to beta-blockers vary considerably. Plasma concentrations can differ by 10 to 20 times between different patients taking the same drug and the same dose.

② Be careful to avoid "withdrawal syndrome." Patients who have used beta-blockers for a long period (more than 2 weeks) and need to discontinue the medication must gradually reduce the dosage over 2 weeks, and should not stop abruptly. Abrupt cessation can generally cause a rebound increase in blood pressure and heart rate within 1 to 10 days (peaking on day 6), and may induce angina or myocardial infarction, or even sudden death, in patients with coronary artery disease. ③ Be alert to the possibility of "first-dose syndrome." Some patients, although their normal heart rate is not slow, may have sinoatrial node dysfunction and cardiac conduction disorders. After using beta-blockers, they may experience excessively slow heartbeats, a heart rate below 50 beats/min, or prolonged cardiac arrest; in severe cases, shock may occur.

④ When beta-blockers are used in combination with diuretics, blood glucose and lipid levels should be monitored.

⑤ Be aware of the adverse reactions of this class of drugs.

What are the adverse reactions of beta-blockers? How can they be avoided or mitigated? The adverse reactions of this class of drugs are as follows:

① Orthostatic hypotension: Beta-blockers reduce sympathetic tone, decrease cardiac output, and reduce peripheral resistance. Therefore, orthostatic hypotension is relatively common, especially in elderly patients, and is more likely to occur at higher doses. To avoid this adverse reaction, patients should move slowly when changing position (avoid sudden standing), and reduce the dose if necessary.

② Bronchospasm: This class of drugs inhibits β2 receptors in bronchial and vascular smooth muscle, causing smooth muscle contraction. This is more common in non-selective β-blockers (such as propranolol), which can cause bronchospasm, worsening asthma attacks and potentially leading to death in severe cases. Therefore, this product is generally contraindicated in patients with bronchial asthma and chronic obstructive pulmonary disease.

③ Worsening of peripheral circulatory diseases: This class of drugs can increase peripheral vascular resistance, causing cold extremities. Therefore, it can worsen pallor, pain, and intermittent claudication symptoms in patients with obliterative peripheral vascular disease, with an incidence of 5%–10%. Thus, this class of drugs should be contraindicated or used with caution in patients with Raynaud's phenomenon and intermittent claudication.

④ Cardiac adverse reactions: These are mainly due to the negative chronotropic, negative conduction, and negative inotropic effects of the drug, leading to sinus bradycardia, atrioventricular block, hypotension, and heart failure. Therefore, choosing β-blockers with endogenous sympathetic activity can reduce negative effects on the heart.

⑤ Neurological adverse reactions: Insomnia, depression, dizziness, headache, lightheadedness, etc. The incidence is approximately 10%, and it is more common with lipid-soluble β-blockers (such as bisoprolol and metoprolol). If the patient can tolerate it, they can continue taking it; if they cannot tolerate it, water-soluble β-blockers can be used to reduce these adverse reactions.

⑥ Others: Fatigue (incidence 5%), nausea (10%), vomiting, myalgia, rash, impotence, etc. It can also interfere with blood glucose and lipid metabolism, increasing blood glucose, cholesterol, triglycerides, and low-density lipoprotein cholesterol. Especially when used in combination with thiazide diuretics, it can significantly increase blood lipids, adversely affecting the long-term prognosis of cardiovascular diseases. Can hypertensive patients with diabetes take beta-blockers?

Beta-blockers can affect glucose metabolism, increase the incidence of severe hypoglycemia, and increase insulin dosage. Furthermore, because the drugs block beta receptors, they lower heart rate, which can mask early symptoms of hypoglycemia (palpitations). Therefore, beta-blockers are often avoided in patients with cardiovascular disease and diabetes. However, numerous clinical studies have now confirmed that sympathetic activity is increased in patients with type 2 diabetes, and beta-blockers have a protective effect in type 2 diabetes patients with hypertension. The UK Prospective Diabetes Study has also confirmed the safety and efficacy of beta-blockers in diabetic patients. The benefits of beta-blockers for diabetic patients may outweigh the consequences of their side effects. However, blood glucose fluctuations must be monitored. Therefore, diabetic patients with clear indications for beta-blocker treatment (such as coronary artery disease or heart failure) should routinely use beta-blockers, preferably selective beta-blockers. This is because non-selective beta-blockers (such as propranolol) reduce insulin secretion by inhibiting pancreatic β-cells, which is detrimental to blood sugar control and can cause insulin resistance in tissues. When diabetic patients overdose and experience hypoglycemia, non-selective beta-blockers can make the hypoglycemia difficult to detect, leading to danger. However, selective beta-blockers (such as metoprolol and atenolol) do not have these adverse effects.

Why can't beta-blockers be stopped abruptly? Long-term use of beta-blockers should not be stopped abruptly because withdrawal syndrome, clinically known as "rebound," is likely to occur. This manifests as a reflex increase in blood pressure, tachycardia, worsening of angina and arrhythmias, and may even lead to acute myocardial infarction and sudden death. This is because after long-term use of beta-blockers, the body's compensatory receptor density is upregulated. Suddenly relieving the beta-blocking effect after stopping the drug will increase receptor excitability. Since the receptors are not downregulated in time, hypersensitivity or hypersensitivity occurs. Sympathetic nerve sensitivity typically begins to increase 24 hours after drug withdrawal, peaks after 6 days, then gradually decreases, returning to normal within 10-14 days. Therefore, the dosage should generally be gradually reduced over 2 weeks until complete discontinuation.

Why can't beta-blockers be used in patients with bradycardia and atrioventricular block?

Beta-blockers work by blocking cardiac β1 receptors, antagonizing sympathetic nerve excitation and the effects of catecholamines, thus slowing heart rate, weakening myocardial contractility, and reducing conduction function, thereby exacerbating bradycardia and conduction block. Therefore, beta-blockers are not suitable for patients with sick sinus syndrome, sinus heart rate below 60 beats/min, or severe atrioventricular block.

Why are beta-blockers contraindicated in patients with bronchial asthma and chronic obstructive pulmonary disease (COPD)? Because beta-blockers not only block cardiac beta1 receptors but also have varying degrees of blockade on bronchial smooth muscle beta2 receptors, especially those with poor selectivity, such as propranolol (Inderal), which can cause more severe effects, leading to bronchial smooth muscle contraction, increased tension, and exacerbated spasm. Metoprolol (Betaloc) and bisoprolol (Concor), which have strong selectivity for beta receptors but weaker effects on beta2 receptors, may also induce bronchial asthma at higher doses. Therefore, beta-blockers are contraindicated in patients with bronchial asthma and COPD.