8. cardiovascular drugs

Chapter 8

Cardiovascular Drugs

Copyright © 2011 Delmar, Cengage Learning

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



• 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



• Heart rhythm– Contractions at regular intervals– Systole is contraction of heart chambers– Diastole is relaxation of heart chambers – Normal heart beat is called normal sinus

rhythm



• 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



• There are 3 major types of blood vessels: arteries, veins, and capillaries– An artery is a blood vessel that carries blood away

from the heart– Veins are low-pressure collecting system that returns

blood to the heart – Capillaries are single-cell-thick vessels that connect

the arterial and venous systems



• Blood pressure– Flows from areas of higher pressure to areas

of lower pressure– Determined by heart rate, stroke volume,

peripheral resistance



• Blood supplies body tissues with oxygen, nutrients, and various chemicals

• Blood transports waste products to various organs for removal from the body

• Blood cells also play an important role in the immune and endocrine systems


Cardiovascular Conditions

• Congestive heart failure is a syndrome that can occur with any disorder that damages or overworks the heart muscle– Conditions that lead to congestive heard failure

include:• Cardiomyopathy (caused by infections, genetic disorders, or

degeneration)• Hypertension• Valvular disease


Cardiovascular Conditions

• Cardiac arrhythmias is a disruption in the cardiac rate or rhythm– Arrhythmias interfere with the work of the heart and

can disrupt cardiac output– Can be caused by changes in the rate, stimulation

from an ectopic focus, or by alterations in conduction of the muscle

– These changes can be caused by electrolyte disturbances, decrease in oxygen delivered to the cells, structural damage, accumulation of waste products, and acidosis


Cardiovascular Disease

• Alterations in blood pressure may result in hypertension (increased blood pressure) or hypotension (decreased blood pressure)– Hypertension results in prolonged force put on the

vessels of the vascular system• Leads to left ventricle thickening

– Hypotension results in the tissues of the body not receiving sufficient amount of oxygenated blood

• Allows wasted products to accumulate and cells to die from lack of oxygen


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


Increasing Force

• 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


Increasing Force

• Positive inotropes– Benzimidazole-pyridazinones:

• Increase the force of contraction• Cause widening of the blood vessels• Side effects include anorexia, lethargy, diarrhea, and

dyspnea


Fixing the Rhythm

• 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, beta-adrenergic blockers, action potential prolongation drugs, and calcium-channel blockers

– For examples of antiarrhythmic drugs refer to Table 8-3 in your textbook


Correcting Constriction

• Vasodilators– Drugs used to dilate arteries and/or veins,

which alleviates vessel constriction and improves cardiac output

– Examples include angiotensin-converting enzyme inhibitors, arteriole dilators, venodilators, and combined vasodilators


Correcting Constriction

• Calcium channel blockers are used to treat CHF and hypertension

• Calcium channel blockers inhibit the movement of calcium through the the myocardial cell membranes and vascular smooth muscle– Decreases the force of cardiac contractions– Side effects include hypotension and anorexia


Losing Fluid

• 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

– For examples refer to Table 8-4 in your textbook


Clot Stopping

• 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


Clot Stopping

• Clopidogrel bisulfate is an oral platelet aggregation inhibitor – May prevent thrombi in cats– Improves circulation in cats following an embolic

event– Side effects are gastrointestinal in nature and include

vomiting and anorexia


Bleeding Control

• 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


Blood Enhancing Drugs

• Affect RBCs

• Affect the production or quality of RBCs

• Examples:– Iron– Erythropoietin


Blood Enhancing

• Erythropoietin is a protein made by the kidneys that stimulates the differentiation of bone marrow stem cells to form red blood cells– Used to treat anemia in animals with chronic renal

failure– Allergic reactions are sometimes seen with

erythropoietin products– Erythropoietin products must be refrigerated


Blood Enhancing

• Cyanocobalamine is B12 and is used to treat B12 deficiencies– Oral forms are not appropriate for small animals

• Folic acid is a B vitamin needed for normal erythropoiesis– May be seen in dogs, cats, and horses due to small

intestinal disease – Very few side effects


8. cardiovascular drugs

Health & Medicine

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heart rate stimulation

heart capillaries

heart veins

heart afterload

dyspnea copyright2011

acidosis copyright2011

volume of blood