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Fundamentals of Pharmacology for Veterinary Technicians Chapter 8 Cardiovascular Drugs © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation. Basic Anatomy and Physiology • The functions of the cardiovascular system include delivery of oxygen, nutrients, and hormones to the various parts of the body • The cardiovascular system also transports waste products to the appropriate waste removal system © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation. Basic Anatomy and Physiology © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation. Basic Anatomy and Physiology • The electrical impulses of the heartbeat originate in the sinoatrial node (SA node) • Heart rate is controlled primarily by the autonomic nervous system: – Stimulation of the parasympathetic nervous system slows heart rate – Stimulation of the sympathetic nervous system increases heart rate © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation. Basic Anatomy and Physiology • Workload of the heart is divided into preload and afterload – Preload: volume of blood entering the right side of the heart – Afterload: force needed to push blood out of the ventricles • If the heart is not working properly, it can compensate by a few mechanisms: – – – – Increase heart rate Increase stroke volume Increase efficiency Enlarge itself © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation. Cardiovascular Drugs • Types of cardiovascular drugs – Positive inotropic drugs: increase the force of myocardial contraction – Negative inotropic drugs: decrease the force of myocardial contraction – Positive chronotropic drugs: increase heart rate by altering the rate of impulse formation at the SA node – Negative chronotropic drugs: decrease heart rate by altering the rate of impulse formation at the SA node – Positive dromotropic drugs: increase the conduction of electrical impulses – Negative dromotropic drugs: decrease the conduction of electrical impulses © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation. Cardiovascular Drugs • Positive inotropes – Cardiac glycosides: • Increase the strength of cardiac contractions, decrease heart rate, have an antiarrhythmic effect, and decrease signs of dyspnea • Side effects include anorexia, vomiting, diarrhea, and cardiac arrhythmias • Examples include digoxin and digitoxin – Catecholamines: • Increase the force and rate of myocardial contraction, constrict peripheral blood vessels, and increase blood glucose levels • Examples include epinephrine, dopamine, dobutamine, and isoproterenol © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation. Cardiovascular Drugs • Antiarrhythmic drugs – Used to correct variation in the normal beating of the heart (which can lead to reduced cardiac output) – Types of antiarrhythmic drugs include local anesthetics, membrane stabilizers, betaadrenergic blockers, action potential prolongation drugs, and calcium-channel blockers – Examples of antiarrhythmic drugs are listed in Table 8-3 © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation. Cardiovascular Drugs • Vasodilators – Drugs used to dilate arteries and/or veins, which alleviates vessel constriction and improves cardiac output – Examples include angiotensinconverting enzyme inhibitors, arteriole dilators, venodilators, and combined vasodilators © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation. Cardiovascular Drugs • Diuretics – Drugs that increase the volume of urine excreted by the kidneys and thus promote the release of water from the tissues (lowers the fluid volume in tissue) – Used in the treatment of hypertension – Categories of diuretics include thiazides, loop diuretics, potassium-sparing diuretics, osmotics, and carbonic anhydrase inhibitors – Examples are listed in Table 8-4 © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation. Cardiovascular Drugs • Anticoagulants – Inhibit clot formation by inactivating one or more clotting factors – Used to inhibit clotting in catheters, to prevent blood samples from clotting, to preserve blood transfusions, and to treat emboli – Examples include heparin, EDTA, coumarin derivatives, aspirin, and blood transfusion anticoagulants © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation. Cardiovascular Drugs • Hemostatic drugs – Help promote the clotting of blood – May be parenteral or topical – Parenteral • Vitamin K1 • Protamine sulfate – Topical • Silver nitrate, hemostat powder, gelfoam gelatin sponges, thrombogen topical thrombin solution © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation. Cardiovascular Drugs • Blood-enhancing drugs – Affect RBCs – Affect the production or quality of RBCs – Examples: • Iron • Erythropoietin © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.