Bio 117 Module 5 (1) PDF

PALAWAN STATE UNIVERSITY College of Sciences BIO 117 - BASIC PHARMACOLOGY Cardiovascular Drugs and Diuretics MODULE 5  Table of Contents Content Page Learning Objectives ……………………………………………………...

PALAWAN STATE UNIVERSITY College of Sciences BIO 117 - BASIC PHARMACOLOGY Cardiovascular Drugs and Diuretics MODULE 5  Table of Contents Content Page Learning Objectives ………………………………………………………. 2 Overview ………………………………………………………………....... 3 I. Drugs used in Heart Failure……………………............................... 4 II. Antiarrhythmic Drugs………....……..……….................................... 15 III. Antianginal Drugs..…………………................................................. 21 IV. Antihypertensive Drugs ………....……..……................................... 26 V. Diuretic Drugs............................................................................... Learning Check 3.1......................................................................... Evaluation ………………………………………………………………….. Grading Rubric.................................................................................... Reflection............................................................................................ References ……………………………………………………………….... 2 Page 1  Learning Objectives After going through in this module, you should be able to:  classify the major cardiovascular drugs in current use by their actions at a cellular level;  describe the cellular actions of drugs that affect the cardiovascular-renal systems;  evaluate the pharmacological basis for the treatment of major cardiovascular diseases and identify the common side effects that these drugs can produce. 3 Page 2  Diastole and systole are two phases of the cardiac cycle. They occur as the heart beats, pumping blood through a system of Discussion blood vessels that carry blood to every part of the body. Systole occurs when the heart contracts to pump blood out, and diastole occurs when I. DRUGS USED IN HEART FAILURE the heart relaxes after contraction. Heart Failure (HF) This is a complex, progressive disorder in which the heart is unable to pump sufficient blood to meet the needs of the body. HF is due to an impaired ability of the heart to adequately fill with and/or eject blood (Figure 3.1). Its cardinal symptoms are dyspnea, fatigue, and fluid retention. It is often accompanied by abnormal increases in blood volume and interstitial fluid, hence the term “congestive” HF because symptoms include dyspnea from pulmonary congestion in left HF, and peripheral edema in right HF (Figure 3.2). Left systolic dysfunction secondary to coronary artery disease is the most common cause of HF, accounting for nearly 70 percent of all cases. The number of newly diagnosed patients with HF is increasing, because more individuals now survive acute myocardial infarction. 4 Figure 3.1 Normal vs. Congestive Heart Page 4 Source: https://www.drugwatch.com/health/cardiovascular-health/congestive-heart-failure/  Discussion I. DRUGS USED IN HEART FAILURE Action Potential Cardiac muscle cells are electrically excitable. However, unlike the cells of other muscles and nerves, the cells of cardiac muscle show a spontaneous, intrinsic rhythm generated by specialized “pacemaker” cells located in the sinoatrial and atrioventricular nodes. The cardiac cells also have an unusually long action potential, which can be divided into five phases (0-4). Figure 3.3 illustrates the major ions contributing to depolarization and polarization of cardiac cells. These ions pass through channels in the sarcolemmal membrane and, thus, create a current. The channels open and close at different times during the action potential. Some respond primarily to changes in ion concentration, whereas others are sensitive to ATP, or to membrane voltage. Purkinje fibers are specialized sets of cells that conduct the passage of action potentials to the apex of the heart, ensuring not only a rapid but also a spatially and temporally coordinated spread of excitation across both ventricles. 5 Figure 3.2 Action potentials from different cell types in the heart. Source: https://thoracickey.com/cardiac- Page 5 electrical-stimulation  Discussion I. DRUGS USED IN HEART FAILURE 6 Figure 3.3 Action potential of a Purkinje fiber Page 6 Source: Lippincott’s Illustrated Reviews: Pharmacology. 4th ed./  Discussion I. DRUGS USED IN HEART FAILURE Goals of pharmacologic intervention in HF The goals are to alleviate symptoms, slow disease progression, and improve survival. Accordingly, six classes of drugs have been shown to be effective: 1) inhibitors of the renin-angiotensin system 2) β-adrenoreceptor blockers 3) diuretics 4) Inotropic agents 5) direct vasodilators 6) aldosterone antagonists 7 Figure 3.4 Symptoms of right and left heart failure Source: https://www.researchgate.net/publication/333431550_A_novel_group_decision_making_model_based _on_neutrosophic_sets_for_heart_disease_diagnosis/figures?lo=1 Page 7  Discussion I. DRUGS USED IN HEART FAILURE Cardiac contraction The force of contraction of the cardiac muscle is directly related to the concentration of free (unbound) cytosolic calcium. Therefore, agents that increase these calcium levels (or that increase the sensitivity of the contractile machinery to calcium) result in an increased force of contraction (inotropic effect). If free cytosolic calcium levels were to remain high, the cardiac muscle would be in a constant state of contraction rather than showing a periodic contraction. Cardiac contraction is the end result of action potentials that are initiated at the sinoatrial node by the spontaneous depolarization of the nodal cells to threshold and the subsequent transmission of triggered action potentials in different cells of the cardiac conduction pathway to the atrial and ventricular muscle. Therapeutic strategies in HF 8 Chronic HF is typically managed by a:  reduction in physical activity  low dietary intake of sodium (