Pharmacology(5) Hypertension, Angina And Heart Failure

Stable angina is a type of chest pain that occurs when the heart muscle doesn't receive enough blood and oxygen. It is typically triggered by physical exertion or emotional stress. The fact that it is relieved by glyceryl trinitrate (also known as nitroglycerin) is a key characteristic of stable angina. Glyceryl trinitrate helps to relax and widen the blood vessels, improving blood flow to the heart and relieving the chest pain. This medication is commonly prescribed to people with stable angina to alleviate their symptoms and prevent further complications.

Organic nitrates are substances that are selective for venous rather than arteriolar smooth muscle. This means that they primarily affect the veins, causing them to dilate and reduce the amount of blood returning to the heart (cardiac preload). By reducing preload, organic nitrates decrease the workload on the heart and improve coronary blood flow. These effects can be beneficial in conditions such as angina, where there is a reduced blood supply to the heart muscle. However, organic nitrates do not have a significant effect on arteriolar smooth muscle, which is responsible for regulating blood flow to various organs and tissues.

The correct answer includes several factors that can contribute to cardiac ischemia. White thrombus, which consists of platelet/fibrinogen/fibrin aggregates, can block the coronary arteries and restrict blood flow to the heart. Spasm of the smooth muscle of the coronary arteries can also narrow the blood vessels and reduce blood flow. Smoking is known to damage the endothelium and promote atherosclerosis, leading to reduced vasodilation and increased risk of ischemia. Additionally, a relative deficiency of endothelium-derived vasodilators can further impair blood flow regulation and contribute to cardiac ischemia.

After organic nitrates administration, nitric oxide is generated, which leads to the relaxation and dilation of blood vessels. This helps in relieving chest pain by improving blood flow to the heart. Additionally, organic nitrates inhibit platelet function, preventing the formation of blood clots. However, organic nitrates do not have a direct effect on non-vascular smooth muscles.

Tolerance to organic nitrates refers to a decrease in the effectiveness of the drugs over time. This loss of efficacy is believed to occur due to the exhaustion of sulfydryl-containing intermediary, which is a long-term event. To counteract this tolerance, intermittent dosage can be used, where the drug is not taken continuously but rather in a scheduled manner. Additionally, in patients who do not experience angina at night, the evening dose can be omitted to further prevent tolerance.

Patients with unstable angina require urgent antiplatelet therapy to prevent further clot formation and reduce the risk of heart attack or stroke. If treated with glyceryl trinitrate, a constant intravenous infusion should be used to maintain a steady level of the medication and provide continuous relief of symptoms. They are also treated with intravenous heparin to prevent blood clot formation and beta-blockers to reduce heart rate and blood pressure. Stopping smoking is always recommended for patients with any form of cardiovascular disease, including unstable angina.

Stable angina is a condition characterized by chest pain or discomfort that occurs when the heart muscle doesn't receive enough blood and oxygen. The management of stable angina involves various approaches. Glyceryl trinitrate is used for pain relief as it helps to relax and widen the blood vessels, improving blood flow to the heart. Acute prophylaxis is achieved by using organic nitrates administered sublingually or buccally, which quickly relieve symptoms by dilating the blood vessels. Longer prophylaxis is achieved by taking oral organic nitrates, which help prevent angina attacks over a longer period of time. Beta-adrenoceptor blockers are also used as they reduce the heart's workload and oxygen demand. Calcium channel blockers are another option as they relax and widen the blood vessels, improving blood flow and reducing chest pain.

Nitrovasodilators provide nitric oxide (NO) in an endothelium-independent manner, meaning they can relax blood vessels even if endothelial function is impaired. This makes them effective in many patients with coronary artery disease, where endothelial function may be compromised.

Glyceryl trinitrate is commonly used for acute prophylaxis, which means it is used to prevent the occurrence of certain medical conditions. In this case, it is administered sublingually, which means it is placed under the tongue for absorption into the bloodstream. It can also be administered in a spray form, which allows for easy and quick absorption. The medication should be taken immediately before undertaking strenuous activity, as it helps to relax and widen blood vessels, reducing the risk of certain conditions like angina or heart attack during physical exertion.

The systemic bioavailability of glyceryl trinitrate from the gut is determined by presystemic drug biotransformation, which means that the drug undergoes biotransformation before reaching the systemic circulation. This process can affect the amount of drug that is available for absorption and distribution in the body. Additionally, the systemic bioavailability of glyceryl trinitrate can be influenced by molecule modification, which refers to changes made to the chemical structure of the drug. Lastly, it is useful for minimizing adverse effects of the sublingual tablets if they are swallowed, suggesting that swallowing the tablets can help reduce potential side effects.

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