Therapeutic Agents for the Cardiovascular System

Chapter 18

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Lecture 04

Therapeutic Agents for the

Cardiovascular System

OBJECTIVES

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• Describe the major components of the cardiovascular system.

Anatomy of the Cardiovascular System

Location and Anatomy of the Heart

• Located in chest cavity between the lungs• Large muscle that:

– Initiates systemic arterial pulse waves– Causes blood to circulate throughout body– Supplies body with nutrients and oxygen

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Location and Anatomy of the Heart (cont’d)

• Arteries are large transport tubes extending from the heart

• Arterioles are smaller tubes• Capillaries are very small tubules that

exchange oxygen and nutrients• Coronary arteries are the vessels responsible

for supplying oxygen to the heart muscle.

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Anatomy of the Heart

6From Gerdin J: Health careers today, ed 5, St Louis, 2012, Mosby

The Heart • Normal heartbeat: 60 to 100 beats/min• Size: Person’s fist• Pericardium: Connective tissue surrounding

heart; anchored by ligaments to chest wall and diaphragm not a layer of the heart wall

• Three main layers: Endocardium, myocardiumand epicardium

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Oxygenation

• Heart has two sides and four chambers – right atrium, right ventricle, left atrium, and left ventricle

• Heart circulates blood through body delivering oxygen, and nutrients to cells, tissues, and organs

• Superior and inferior vena cava returning blood to the heart

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Oxygenation (cont’d)

• Superior vena cava brings blood from upper portion of body

• Inferior vena cava brings blood into heart from lower portion of body

• Blood travels through right atrium to right ventricle

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Blood Oxygenation

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Oxygenation (Cont.)

Right ventricle contracts → sends deoxygenated blood to

pulmonary arteries → then to lungs where blood is

oxygenated → Left atrium receives oxygenated blood

from lungs via pulmonary veins → Left ventricle contracts

→ blood sent to aorta11

Circulation of Blood Through the Body

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Cardiac Conduction System • Cardiac conduction system provides electrical charge that

makes heart pump• It is run by two nodes: Sinoatrial (SA) node

Upper right atrium wall Sends signal to AV node in septum between right atrium and right ventricle,

then throughout muscle fibers

Atrioventricular (AV) node From the atrioventricular node the impulse goes to the ventricles to initiate

a ventricular beat by stimulation of the bundle branches and Purkinje fibers

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The Cardiac Cycle

• Cardiac cycle is series of events that occur for one complete heartbeat

• There are two sequences: Systole

Contraction phase

Diastole Relaxation phase

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Regulation of the Heart • Parasympathetic and sympathetic branches of ANS

have opposite effects on heart rate• Norepinephrine and epinephrine released during

exercise increase heart rate• Blood pressure: Force exerted by blood against inner

blood vessel walls• Cardiac output (CO): Increase in CO means increased

blood pressure and flow• Increased blood volume may cause increased blood

pressure– BP expressed as systolic pressure over diastolic pressure

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Peripheral Resistance • Peripheral Resistance:

– Resistance to blood flow due to blood viscosity and amount of force needed

• Vasoconstriction: Decreased blood vessel diameter• Vasodilation: Increased blood vessel diameter• Hormones important in regulating blood pressure

– In low pressure, kidneys release renin; enzyme reactions create angiotensin II

• Hormones increase sodium and water retention in kidneys

• Fluid retention leads to increased blood volume (renin-angiotensin-aldosterone system)

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Therapeutic Agents for the Cardiovascular System OBJECTIVES

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1. List the primary symptoms of conditions associated with dysfunction of the cardiovascular system.

2. Recognize drugs used to treat the conditions associated with the cardiovascular system discussed in this chapter.

3. Write the generic and trade names for the drugs discussed in this chapter.

4. List appropriate auxiliary labels when filling prescriptions for drugs discussed in this chapter.

Common Medication Classes Used to Treat Cardiac Conditions

• ABCD is the mnemonic forA. Angiotensin-Converting Enzyme (ACE) inhibitors Helps reduce blood pressure by dilating arteries.

B. Beta-blockers Blocks both norepinephrine and epinephrine from binding to beta-adrenergic

receptors. This reduces the heart rate which can help lower BP and regulate heartbeat in people with tachycardia.

C. Calcium channel blockers Act by reducing the calcium intake of the heart muscle and the blood vessels.

D. Diuretics Classification not used in the treatment of hyperlipidemia An agent that increases urine output and excretion of water form the body.

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Common Medication Classes Used to Treat Cardiac Conditions (cont’d)

• ACE inhibitors:– Reduce blood pressure by dilating arteries – End in “-pril”– Side effect dry, hacking cough

• Angiotensin II receptor antagonists:– Also known as angiotensin II receptor blockers [ARBs]– Very similar to ACE inhibitors; works by inhibiting angiotensin

to reduce blood pressure – End in “-artan”

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Common Medication Classes Used to Treat Cardiac Conditions (Cont.)

• Beta blockers:– Block norepinephrine and epinephrine, which

reduces heart rate – End in “-olol”

• Calcium channel blockers: – Reduce calcium intake of the heart, which

decreases blood pressure due to vasodilatation

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Conditions Affecting the Cardiovascular System

• Heart conditions include:– Hyperlipidemia

• Lipitor, Niaspan ER, and Questran– Hypertension – Myocardial infarction (MI)– Prehypertensive state– Thrombosis– Drug Questran binds to bile acids in the GI tract,

preventing reabsorption to lower cholesterol levels.

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Hypertension• Hypertension is persistent high blood pressure• “Silent killer”; there are no obvious signs of its

presence• Is result of various factors, such as diseased

heart or kidneys not working properly, causing edema

• Risk factors include: genetics, age, gender, race, lifestyle, diet, anxiety, alcohol consumption, and sodium intake

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Hypertension (Cont.)

• High blood pressure: Systolic more than 140 mm Hg• Diastolic readings: Three categories of hypertension• Systolic readings: Two categories of hypertension• Four-step approach based on severity of condition• Diet with or without medication (leading contributors

of hypertension include food high in fat, sodium, tyramine)

• To reduce hypertension: Reduce salt and alcohol intake, exercise, quit smoking

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Treatment of Hypertension • Main agents: Antihypertensives:

– Methyldopa– Doxazosin– Clonidine– Terazosin– Prazosin

• Other agents: Diuretics and Vasodilators• If medication required, diuretics are initial drug therapy

– Other agents: Angiotensin-converting enzyme (ACE) inhibitors, beta-blockers, and calcium channel blockers

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Hypotension• Low blood pressure• Orthostatic hypotension: Standing up quickly

from lying position• Side effects: Syncope (fainting), vertigo (dizziness)

fainting upon standing• Treatment: Medication adjustment, increased salt

intake, drink more water, move/stand slowly• Drug treatment:

– Fludrocortisone (which increases blood volume)– Midodrine (which raises blood pressure)

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Hyperlipidemia• Increase of lipids in bloodstream; precursor to

atherosclerosis (hardening of arteries).• Purpose of cholesterol: Vital for making

steroid hormones and cell membranes• Ingestion of high fat foods: Too much

cholesterol and fatty acids; body cannot eliminate

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Hyperlipidemia (Cont.) • Fatty substances float through bloodstream;

latch onto large arteries and middle-sizedarteries of heart and brain; body cannot eliminate

• Generic test given for cholesterol levels– Low is below 200 mg/dL– Borderline high is 200 to 239 mg/dL

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Hyperlipidemia (Cont.)

• High: 240 mg/dL• In-depth look:

– Low-density lipoprotein (LDL)– High-density lipoprotein (HDL)– Very-low–density lipoproteins (VLDLs): Precursor

to LDL

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Factors Influencing Hyperlipidemia • Family history, lifestyle habits, and patient’s

personal medical history• Good cholesterol HDL: Transporters of fat

from tissues• Bad cholesterol LDL: Carry around lipids (fat)

that can attach to artery walls, causing atherosclerosis

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Drug Treatment for Hyperlipidemia• Antihyperlipidemics

– Bile acid sequestrants– Hydroxymethylglutaryl-coenzyme A (HMG-CoA)

reductase inhibitors (“statins”) – Fibrates

• Statins raise HDL and lower LDL and VLDL• Statins may be toxic to Liver• Niacin added to other drug therapies some

formulations of Niacin cause flushing30

Coronary Artery Disease • Coronary artery disease (CAD) is associated with

atherosclerosis, the buildup of lipids (cholesterol) in arteries

• Atherosclerosis is linked to high blood pressure • Fatty deposits build up, thrombus forms, and

artery blocked: Results in myocardial infarction• Nitrates, beta-blockers, calcium channel blockers

(CCBs), and bile acid sequestrants• Nitrates are used to treat angina, reduce the

workload of the heart and dilate the arteries

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Coronary Artery Disease (Cont.) • Risk factors:

– Hypertension – Age, gender, race– Genetics– Factor alterations:

• Fatty diet• No exercise• Smoking• Stress

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Angina Pectoris • Three types:

– Classic– Variant– Unstable

• Classic angina: Short ischemic episodes of pain and mild deficiency of oxygen– Pain: Chest, neck, arms, teeth, jaw– Can occur after exercise or excessive activity– Decreased blood flow to heart results in chest pain,

minor to severe

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Angina Pectoris (Cont.) • Variant angina:

– Spasms of coronary artery– Very painful and may occur even at rest

• Unstable angina:– History of anginal attacks– Obstruction of arteries, increases over time

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Treatment of Angina Pectoris • Treatment:

– Nitrates, Nitroglycerin (NTG)– Lifestyle changes– Surgery to bypass blockage– NTG ointment is available in 1g,30g,and 60g.

Doses are measured in half (½) to 2-inch segments similar to toothpaste. NTG ointment is applied to the chest skin.

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Drug Treatment for Angina Pectoris • Common agents include nitrates, calcium

channel blockers, beta-blockers• Most prescribed are nitroglycerin (sublingual

tablets)• Dosage forms for nitroglycerin include

capsules, topical patches, paste, sublingual spray

• Sublingual tablets and injectable forms used in emergency only

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Nitrates: Drug Action • Vasodilators dilate arteries to permit increase

of blood flow through heart muscle• They reduce workload of heart• Isosorbide and nitroglycerin: Treat angina• Sublingual tablets: Very effective; rapid

absorption; bypass gastrointestinal system; enter directly into bloodstream– Drug not inactivated by stomach acid– Faster onset of action

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Nitrates: Drug Action (Cont.) • Nitroglycerine is only good for 6 months after opening

container• Must be kept in dry area in light-protected glass container

to prevent breakdown• Patches, applied once daily, are taken off at bedtime• Ointment tubes available in 60 g, 30 g, and 1 g (unit dose)• Translingual spray: Patient sprays one or two metered

doses under tongue with maximum of three sprays per 15-minute period

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Thrombotic Events • Formation of a clot blocking blood flow is thrombosis• Some clots are bad (overactive clotting mechanism)• Embolus: Clot broken away from thrombus, lodged and

creating blockage• Treatment: Supportive stockings, standing/walking on

a regular basis to facilitate circulation• Drug treatment: Anticoagulants or thrombolytics

– Anticoagulant: Warfarin interferes with vitamin K synthesis

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Myocardial Infarction and Transient Ischemic Attack

• Blood flow is entirely blocked because of thrombus, results in death of that part of the heart

• A massive infarction permanently weakens heart• Treatment: Cardiac rehab, dietary changes; beta-

blockers, ACE inhibitors• Transient ischemic attack (TIA): Short period of

reduced oxygenation to brain; can last a few minutes or occur throughout day

• Treatment: Reduce risk factors; antiplatelet medication, anticoagulants; surgery

• (MI) also known as a heart attack40

Arrhythmia• Irregular heartbeats: Dysrhythmias• Pacemaker: SA node• Chemical or oxygen imbalance influences

pacemaker, resulting in dysrhythmias• Short-term treatment: Emergency room• Long-term treatment: Medications

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Drug Treatment for Arrhythmias

• Agents: Work on conduction system to induce regular heartbeats

• Lidocaine: Used in emergency situations after MI and other conditions

• Quinidine sulfate & Procainamide: Decrease speed of conduction system; used for tachycardia, and other arrhythmias

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Heart Failure • Heart failure (HF) is a progressive disease. Therefore

there is no cure. – Lanoxin is most commonly prescribed.

• Digibind prescribed to treat an overdose of Lanoxin• Heart cannot pump vigorously, & delivers less blood

throughout body• Complication: Edema (kidneys retain more fluid)

making the heart work harder• Most common treatments:

– Cardiac glycosides: Digoxin– Diuretics for edema

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Diuretics Used for Heart Failure–Related Edema

• Thiazides, loop diuretics: Large potassium loss in urine (potassium supplements used) typically used for the treatment of hypertension

• Diuretics given with agents to decrease effects of sodium retention– Example is hydrochlorothiazide (HCTZ)

• Potassium-sparing diuretics: Triamterene/HCTZ

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Hypertension

• Patients with hypertension should be aware of decongestants, nonsteroidal anti-inflammatory drugs (NSAIDs) and antihistamines.

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Questions?

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