Anti-anginal drugs are medications designed to relieve or prevent angina pectoris, a condition characterized by chest pain or discomfort resulting from reduced blood flow to the heart muscle. These drugs aim to improve the blood supply to the heart, reduce the workload on the heart, and alleviate the symptoms of angina. Anti-anginal drugs can be classified into various categories, and their mechanisms of action may include vasodilation of coronary arteries, reduction of cardiac workload, and improvement of myocardial oxygen supply and demand balance. These medications play a crucial role in managing angina and improving the quality of life for individuals with coronary artery disease.
Classification of Anti-Anginal Drugs
1. Nitrates and Nitrites:
Nitrates: Nitrates refer to medications such as nitroglycerin, isosorbide dinitrate, and isosorbide mononitrate. These drugs are vasodilators that release nitric oxide, leading to the relaxation of blood vessels, especially veins. This vasodilation reduces the workload on the heart, improving blood flow to the heart muscle and alleviating symptoms of angina.
Nitrites: Nitrites are less commonly used in modern medicine but historically have been associated with treating angina. They share some vasodilatory properties with nitrates.
Examples: Nitroglycerin, isosorbide dinitrate, and isosorbide mononitrate.
Mechanism: Vasodilation, especially in coronary arteries, reduces cardiac preload and afterload.
2. Beta-Blockers
Beta-blockers, also known as beta-adrenergic blocking agents, are a class of medications that interfere with the effects of the hormone adrenaline (epinephrine) and related substances. These drugs primarily block the action of beta receptors, which are found in various tissues, including the heart and blood vessels.
Examples: Atenolol, metoprolol, propranolol.
Mechanism: Reduction of heart rate, contractility, and oxygen demand.
3. Calcium Channel Blockers
Calcium channel blockers (CCBs), also known as calcium antagonists, are a class of medications that inhibit the entry of calcium ions into cells, particularly cardiac and smooth muscle cells. By blocking calcium channels, these drugs reduce calcium influx, leading to vasodilation and decreased heart contractions force and rate.
Examples: Amlodipine, diltiazem, verapamil.
Mechanism: Vasodilation and reduced cardiac workload by blocking calcium channels.
4. Potassium Channel Openers
Potassium channel openers are a class of medications that selectively activate potassium channels, leading to the efflux of potassium ions from cells. These drugs primarily affect cellular membrane potential and are used for various therapeutic purposes, including treating cardiovascular conditions.
Example: Nicorandil
Mechanism: Potassium channel openers function by activating specific channels in cell membranes, promoting the outflow of potassium ions. This results in cell membrane hyperpolarization, diminishing cell excitability, especially in smooth muscle cells of blood vessels and cardiac muscle cells. Hyperpolarization induces vasodilation, lowering blood vessel tone and reducing the heart’s workload.
Pharmacological Actions of Anti-anginal drugs
1. Nitrates and Nitrites:
Rapid relief of angina symptoms.
Dilatation of coronary arteries and veins, reducing preload and afterload.
Improved oxygen supply to the heart.
2. Beta-Blockers:
Reduction of heart rate and contractility.
Decreased myocardial oxygen demand.
It improved exercise tolerance.
3. Calcium Channel Blockers:
Dilation of coronary arteries and peripheral arterioles.
Reduced myocardial oxygen demand.
Improved oxygen supply to the heart.
4. Potassium Channel Openers:
Potassium channel opner.
Vasodilation leads to a decrease in blood vessel tone
Dose of Anti-anginal drugs
1. Nitrates and Nitrites:
Sublingual Nitroglycerin: 0.3 to 0.4 mg as needed for acute relief.
Isosorbide Dinitrate: 5 to 40 mg orally, two to three times daily.
2. Beta-Blockers:
Atenolol: 25 to 100 mg orally once daily.
Metoprolol: 50 to 200 mg orally once or twice daily.
3. Calcium Channel Blockers:
Amlodipine: 5 to 10 mg orally once daily.
Diltiazem: 120 to 360 mg orally in divided doses.
4. Potassium Channel Openers:
Initial dose: 10-20 mg orally twice daily.
Indications of Anti-anginal drugs
1. Nitrates and Nitrites:
Acute relief of angina symptoms.
Prophylaxis of angina.
2. Beta-Blockers:
Chronic stable angina.
Acute coronary syndromes.
Hypertension.
3. Calcium Channel Blockers:
Chronic stable angina.
Variant (Prinzmetal’s) angina.
Hypertension.
4. Potassium Channel Openers:
Chronic angina.
Contraindications of Anti-anginal drugs
1. Nitrates and Nitrites:
Severe anemia.
Hypersensitivity.
2. Beta-Blockers:
Asthma or severe chronic obstructive pulmonary disease (COPD).
Heart block.
3. Calcium Channel Blockers:
Severe hypotension.
Heart failure.
4. Ranolazine:
Severe Aortic Stenosis
Heart Failure
