cardiac glycosiides

What digitalis came from

Purple and white foxglove plant

What is digitalis used for originally

To alleviate dropsy

What is digitalis used for now

heart failure (HF), also known as cardiac failure (CF), and previously referred to as congestive heart failure (CHF)

Heart failure

When the heart muscle (myocardium) weakens and enlarges, it loses its ability to pump blood through the heart and into the systemic circulation

Causes of heart failure

chronic hypertension, myocardial infarction (MI), coronary artery disease (CAD), valvular heart disease, congenital heart disease, and arteriosclerosis

Left side heart failure

left ventricle does not contract sufficiently to pump the blood returned from the lungs and left atrium out through the aorta into the peripheral circulation

Effects of left side heart failure

this causes excessive amounts of blood to back up into the lung tissue. Usually the patient has shortness of breath (SOB) and dyspnea

Right side heart failure

occurs when the heart does not sufficiently pump the blood returned into the right atrium from the systemic circulation

effects of right side heart failure

the blood and its constituents are backed up into peripheral tissues, causing peripheral edema.

1st stage heart failure

Breathlessness or tiredness ( walk, jog or going up stairs)

2nd stage heart failure

Comfortable wen resting but heart races when walking a block or talking the stairs

Third stage heart failure

Palpation or tiredness with simple talks like getitng up the sofa and walking over to the kitchen

forth stage heart failure

Heart and breath go faster even at rest and tiredness even while sitting

Effect of natural glycosides

inhibits the sodium potassium pump, resulting in an increase in intracellular sodium

Effect of increasing of intracellular sodium

influx of calcium, causing the cardiac muscle fibers to contract more efficiently

Positive effect of digitalis

Positive inotropic action (increases myocardial contraction stroke volume)

negative effects of digitalis

Negative chronotropic action (decreases heart rate)

Another negative effect of digitalis

Negative dromotropic action (decreases conduction of heart cells)

Use of cardiac gycosides

correct atrial fibrillation and atrial fluters

Cardiac dysrhythmia

with of rapid uncoordinated contractions of atrial myocardium

Atrial flutters

cardiac dysrhythmia with rapid contractions of 200 to 300 beats/ min

How cardiac glycosides work

accomplished by the negative chronotropic effects (decreased heart rate) and negative dromotropic effects (decreased conduction through the atrioventricular [AV] node)

Absorption of digoxin

oral tablet form is 70%. The rate is 90% in liquid and capsule form.

Protein binding power

30%

Half life

30-40 hours

Metabolism for digoxin

metabolized by the liver, and 50% to 70% is excreted by the kidneys mostly unchanged.

What affects excretion of digoxin

Kidney dysfunction

What can alter metabolism of digoxin

Thyroid dysfunction

what to do if patient has failing hear

cardiac glycosides increase myocardial contraction, which increases cardiac output and improves circulation and tissue perfusion

Drugs that treat HF

Vasodilators, Angiotensin-converting enzyme (ACE) inhibitors Angiotensin II receptor antagonists (blockers) Diuretics (thiazides, furosemide) Spironolactone (Aldactone) Some beta blockers

Vasodilators

decrease venous blood return to the heart resulting in a decrease in cardiac filling, ventricular stretching (preload), and oxygen demand on the heart.

Preload

Volume of blood in ventricles at end of diastole

Afterload

Resistance left ventricles must overcome to circulate

First act of arteriolar dilatators

reduce cardiac afterload, which increases cardiac output

2nd act of arteriolar dilators

to dilate the arterioles of the kidneys, which improves renal perfusion and increases fluid loss

3rd act of arteriolar dilators

to improve circulation to the skeletal muscles

ACE inhibitors

dilate venules and arterioles, improving renal blood flow and decreasing blood fluid volume

Angiotensin II receptor blockers (ARBs),

approved for HF in patients who cannot tolerate ACE inhibitors

Diuretics

first-line drug treatment for reducing fluid volume

Spironolactone

a potassium-sparing diuretic, is used in treating moderate to severe HF

Aldosterone

This promotes body loss of potassium and magnesium needed by the heart and increases sodium and water retention.

Antianginal Drugs

used to treat angina pectoris.

Spironolactone

blocks the production of aldosterone

angina pectoris

condition of acute cardiac pain caused by inadequate blood flow to the myocardium due to either plaque occlusions within or spasms of the coronary arteries.

Reason for Angina pectoris

decreased blood flow, there is a decrease in oxygen to the myocardium, which results in pain.

Classic Angina

Occurs with predictable stress or exertion

Unstable Angina

Occurs frequently with progressive severity unrelated to activity; unpredictable regarding stress/exertion and intensity

Variant angina

Occurs during rest The first two types are caused by a narrowing or partial occlusion of the coronary arteries; variant angina is caused by vessel spasm (vasospasm)

Nitrates

They affect coronary arteries and blood vessels in the venous circulation.

How does nitrate work

Cause generalized vascular and coronary vasodilation, which increases blood flow through the coronary arteries to the myocardial cells

Side effects of nitrates

the patient may experience dizziness, faintness, or headache as a result of the peripheral vasodilation

Most common route for nitrates

Sublingual

First pass metabolism for nitrates

Liver

Where is nitrate absorbed directly

internal jugular vein and the right atrium

How much nitrates is absorbed and where

40% to 50% of nitrates absorbed through the gastrointestinal (GI) tract are inactivated by first-pass metabolism in the liver.

First pharmacodynamic of nitrates

s directly on the smooth muscle of blood vessels, causing relaxation and dilation.

2nd pharmacodymanic of nitrates

It decreases cardiac preload (amount of blood in the ventricle at the end of diastole) and afterload (peripheral vascular resistance) and reduces myocardial O2 demand.

3rd phramacodynamic of nitrates

With dilation of the veins, there is less blood return to the heart, and with dilation of the arteries, there is less vasoconstriction and resistance.

What does beta blockers block

the beta1- and beta2-receptor sites.

How does beta blockers block this

decrease the effects of the sympathetic nervous system by blocking the action of the catecholamines (epinephrine and norepinephrine), thereby decreasing the heart rate and blood pressure

What are beta blockers used as

antianginal, antidysrhythmic, and antihypertensive drugs.

What are calcium channel blockers used for

stable and variant angina pectoris, certain dysrhythmias, and hypertension

How does calcium channel blockers work

activates myocardial contraction, increasing the workload of the heart and the need for more oxygen.

How does calcium channel blockers help the body

relax coronary artery spasm (variant angina) and relax peripheral arterioles (stable angina), decreasing cardiac oxygen demand

What is cardiac dysrhythmia

any deviation from the normal rate or pattern of the heartbeat.

bradycardia

heart rates that are too slow

tachycardia

Heart rates that are too fast

dysrhythmia

disturbed heart rhythm

arrhythmia

absence of heart rhythm

What is sodium channel blocker

decreases sodium influx into cardiac cells. Responses to the drug are decreased conduction velocity in cardiac tissues; suppression of automaticity, which decreases the likelihood of ectopic foci; and increased recovery time (repolarization or refractory period

Class 1A sodium channel blocker

slows conduction and prolongs repolarization (quinidine, procainamide, disopyramide)

Class 1B sodium channel blocker

slows conduction and shortens repolarization (lidocaine, mexiletine HCl)

Class 1C sodium channel blocker

prolongs conduction with little to no effect on repolarization (flecainide)

What are class 2: Beta blocker

decrease conduction velocity, automaticity, and recovery time (refractory period).

Examples of Class 2 Beta blocker

propranolol (Inderal), acebutolol (Sectral), esmolol (Brevibloc), and sotalol (Betapace)

What are class 3: Drugs that prolong repolarization

prolong repolarization and are used in emergency treatment of ventricular dysrhythmias when other antidysrhythmicsare ineffective

Examples of class 3

Amiodarone (Cordarone) increases the refractory period (recovery time) and prolongs the action potential duration (cardiac cell activity).

What are class 4: calcium channel blocker

It increases the refractory period of the AV node, which decreases ventricular response. Verapamil is contraindicated for patients with AV block or HF

Examples of Class 4: calcium channel blocker

The fourth class consists of the calcium channel blockers verapamil (Calan, Isoptin) and diltiazem(Cardizem)