Mechanisms of Action and Practices of Six Major Classes of Drugs for Coronary Artery Disease: A Comprehensive Analysis of Nitrates, Beta-Blockers, and Anticoagulation Therapy

32. What are the general effects of various medications for treating coronary heart disease? Many people suffering from angina have experienced the following distress and confusion: When they have an angina attack, they go to the hospital, only to be prescribed three or four medications. Taking so many medications every day is not only inconvenient but also difficult for their stomachs. Over time, it becomes hard to adhere to the regimen. So, they gradually reduce the number of medications, eventually resorting to only taking nitrates, which dilate coronary arteries. So, why do doctors prescribe so many medications for angina patients? Actually, there are six main categories of medications used to treat angina, each with a different function and none of them are interchangeable. Their effects may include improving symptoms, protecting the heart, preventing thrombosis, or stabilizing plaques... For an angina patient, at least three to four of these are essential. The remaining medications depend on the individual's condition. Therefore, angina patients are destined to take a variety of medications. However, I believe that your inability to adhere to medication regimens mainly stems from a lack of understanding of their functions. Once you understand the benefits of each medication, you can continue taking them. So, let's learn about the medications for angina! (1) Nitrate preparations. These mainly include nitroglycerin, isosorbide dinitrate (Isosorbide dinitrate), 5-mononitrate sorbitol, long-acting nitroglycerin preparations, etc. Although nitrate drugs cannot effectively reduce the mortality rate of patients with acute myocardial infarction, they can effectively relieve coronary artery spasm, relieve angina symptoms, and reduce the frequency of attacks. The main indications are the prevention and treatment of angina. (2) β-blockers (β-blockers). Commonly used preparations include bisoprolol (Concor), Bosu, metoprolol (Betaloc), atenolol (Aminoxin), etc. Clinically, they mainly reduce myocardial oxygen demand by slowing the heart rate and reducing myocardial contractility, thereby achieving the purpose of treating angina. These drugs are only suitable for stable angina, and should be used with caution in unstable angina and are contraindicated in variant angina. β-blockers can effectively reduce cardiac events in secondary prevention after myocardial infarction, and are also the first choice for patients with stable angina in terms of reducing morbidity and mortality. (3) Calcium channel blockers. Commonly used preparations include verapamil, nifedipine, diltiazem, and nicardipine. Long-acting or sustained-release dihydropyridine calcium channel blockers and non-dihydropyridine calcium channel blockers can relieve symptoms in patients with stable angina without increasing the incidence of adverse cardiac events. Calcium channel blockers are effective in treating variant angina. (4) Angiotensin-converting enzyme inhibitors. Commonly used ones include lodin, mononitrate, and captopril. They have good short-term and long-term efficacy in reducing mortality in patients with myocardial infarction and reversing ventricular remodeling. (5) Antiplatelet drugs. Such as aspirin, dipyridamole, and sulfadiazine. (6) Lipid-lowering drugs. Such as niacin, pravastatin (Pracou), fluvastatin (Lescol), atorvastatin (Lipitor), and simvastatin (Zocor). Lipid-lowering drugs have the effect of stabilizing atherosclerotic plaques, and their application has good benefits for patients with coronary heart disease.

33. How to use nitrate drugs to treat angina pectoris. Nitrates have the longest history as anti-anginal drugs. To date, they are still recognized as one of the most effective and widely used anti-anginal drugs. They can dilate coronary arteries and increase coronary blood flow. Intravenous infusion of nitroglycerin has an immediate effect, and the effect is constant when administered at a constant rate. In cases of unstable angina pectoris, frequent or severe angina attacks should be treated under the supervision of a doctor. (2) Used during the interictal period (remission period) of angina pectoris attacks. Oral nitrates for the prevention and treatment of angina pectoris include: Isosorbide dinitrate (Isosorbide dinitrate) is relatively completely absorbed orally, with a significant first-pass effect in the liver, taking effect in 15-40 minutes and lasting for 4-6 hours. The dosage should be individualized. Isosorbide mononitrate: There is no first-pass effect in the liver when taken orally. Brand names: Demaining, Lizhuxinle, Imdrol, long-acting isoradine, etc. Nitroglycerin is easily deactivated, especially after exposure, so it should be stored in a brown bottle for no more than half a year. Headaches may occur when using nitrates, often described as throbbing or pulsating pain due to intracranial vasodilation. These headaches usually subside spontaneously with continued use, typically within 7–10 days. Patients with severe symptoms may take analgesics. However, 20%–30% of patients cannot tolerate nitrates.

34. How to use beta-blockers to treat angina pectoris? Beta-blockers reduce myocardial oxygen consumption by lowering heart rate, weakening myocardial contractility, and reducing myocardial tension, thereby improving myocardial ischemia and hypoxia and controlling angina pectoris. They are suitable for exertional angina pectoris. Commonly used drugs include: metoprolol (Metoprolol, brand name Betoprolol), atenolol (Metoprolol), and bisoprolol (brand names Concord, Bosu). Beta-blockers are the "cornerstone" of anti-anginal drug therapy, with an efficacy rate of 80% to 90% in treating exertional angina pectoris. Within a certain range, the efficacy is dose-dependent. Adjusting the appropriate dose is key to achieving satisfactory results. Generally, heart rate is an important indicator for dose adjustment. Ideally, the resting heart rate should be reduced to around 60 beats/min. Even if the heart rate drops to around 55 beats/min, as long as the heart rate increases during exercise and there is no discomfort, it is not an indication for reducing or stopping the medication. Patients with coronary artery disease and angina should use beta-blockers under the guidance of a doctor whenever possible. Long-term use of beta-blockers can reduce the incidence of cardiovascular events and mortality, and is an important component of secondary prevention of coronary artery disease. It is worth noting that beta-blockers have a synergistic effect with nitrates; the starting dose should be reduced. If beta-blockers need to be discontinued, the dose should be gradually reduced (as rebound may occur). Patients with heart failure, bradycardia, or bronchial asthma should not use beta-blockers. Beta-blockers should not be used alone in cases of coronary artery spasm (such as typical variant angina), as they can block the vasodilatory effect of β2 receptors, thereby losing the antagonistic effect of α receptors and potentially causing coronary artery spasm.

35. How to use calcium channel blockers to treat angina pectoris: Calcium channel blockers dilate arteries, inhibit cardiac contraction, reduce myocardial oxygen consumption, and relieve coronary artery spasm. They are suitable for treating all types of angina pectoris, and are most suitable for variant angina pectoris. They should be used under the guidance of a doctor.

36. How to use anticoagulants to treat angina pectoris. Anticoagulants are represented by heparin. Their anticoagulant mechanism mainly involves binding to antithrombin II in plasma to form a complex, thereby accelerating the inhibition of thrombin and exerting their effect. The main adverse reaction is bleeding. A low-molecular-weight heparin has been produced; although its anticoagulant activity is weaker than that of unfractionated heparin, it has a stronger antithrombotic effect and fewer bleeding adverse reactions, making it a promising heparin-based antithrombotic drug.

37. How to use antiplatelet drugs to treat angina pectoris? Antiplatelet drugs can inhibit platelet aggregation and prevent or inhibit thrombus formation. Aspirin inhibits cyclooxygenase, rendering platelets inactive and reducing the production of prostaglandins GZ, H2, and thromboxane A2. Ticlopidine (Ticlopidine) is a new and potent antiplatelet drug with significant antithrombotic effects. It inhibits all stages of platelet aggregation. However, it is relatively expensive, and serious adverse reactions include agranulocytosis and thrombocytopenic purpura. Therefore, hematological monitoring should be performed during use. It can be considered for patients allergic to aspirin.

38. Rational Clinical Use of Warfarin: Indications for warfarin anticoagulation therapy include patients with atrial fibrillation and high-risk factors for coronary heart disease and stroke, prevention of venous thrombosis and pulmonary embolism, and post-mechanical heart valve replacement surgery. Warfarin is a coumarin-based oral anticoagulant that inhibits the carboxylation of glutamate, a vitamin K-dependent clotting factor, preventing these clotting factors synthesized in the liver from exerting their clotting effect. After oral warfarin administration, its effect on the extrinsic coagulation system (prothrombin time; PT) must be monitored. Clinically, the standardized PT, i.e., the international normalized ratio (INR), is used to adjust the warfarin dosage. The recommended initial dose of warfarin for Chinese patients is 3 mg. Elderly patients over 75 years of age and high-risk patients with bleeding tendencies should start with 2 mg, once daily. The target INR depends on the patient's condition, generally 2.0–3.0, and 1.6–2.0 for the elderly. The dosage for the next dose should be determined based on the INR value. INR should be measured at least 3 times during the first week, then once a week until the fourth week. Once the INR reaches the target value and stabilizes (two consecutive measurements within the target range for treatment), it can be measured once every 4 weeks.