Cardiac Glycosides and Inodilators Flashcards

1
Q

What two clinical conditions in veterinary practice would you use cardiac glycoside for treatment

A

dilated cardiomyopathy and endocardiosis

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2
Q

What symptoms are shown with Class 1 congestive heart failure?

A

only strenous exercise is limited

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3
Q

What symptoms are shown with Class 2 congestive heart failure?

A

fatigue, shortness of breath, coughing on exercise

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4
Q

What symptoms are shown with Class 3 congestive heart failure?

A

comfortable at rest but excercise is minimal

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5
Q

What symptoms are shown with Class 4 congestive heart failure?

A

no capacity for exercise, clinical signs at rest

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6
Q

What drugs can be used for class 2-4 congestive heart failure?

A

digoxin, pimobendan, ACE inhibitors, and other inotropic drugs

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7
Q

What is the goal of drugs used to treat congestive heart failure?

A

the goal is to increase stroke volume

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8
Q

What is the problem with digoxin?

A

getting the dose right

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9
Q

What form of digoxin is the best use?

A

in a liquid form

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10
Q

What is the mode of action of glycoside?

A

Glycoside → inhibition of Na/K exchange → Increased Na concentration → decreased Na/Ca exchange → Increased Ca concentration → increased contraction and rate

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11
Q

What are the major actions of cardiac glycosides?

A

Positive inotropic action - increased force

Negative chronotropic effect - slowing of the heart

Negative dromotropic effect - slowing conduction of the AV node

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12
Q

How do cardiac glycosides create a negative chronotropic effect?

A

they stimulate the vagus nerve and also improve baroreceptor sensitivity countering sympathetics

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13
Q

What is the half-life and elimination method of digoxin in dogs?

A

Half-life - 23-39 hours

Elimination - mainly renal

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14
Q

What is the half-life and elimination method of digoxin in cats?

A

Half-life - 25-78 hours

Elimination - renal

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15
Q

What is the half life and steady state of digoxin in horses?

A

Half-life - 13-23 hours

Elimination - renal

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16
Q

What are the deleterious effcts of digoxin on the heart rhythm and GI tract?

A

Auricular arrhythmias/tachycardia

AV block

Ventricular arrhythmias/extra-systole/pulses bigemiini/Ventricular fibrillation

Gi disturbances - anorexia, vomiting, diarrhea

17
Q

Generally how do you treat digoxin toxicity?

A

stop giving the drug and allow it to be cleared and give IV fluids to maximize renal clearance

18
Q

How do you treat ventricular arrhythmias due to digoxin?

A

treat with lidocaine, phenytoin, and propanolol

19
Q

What inodilator did we discuss in class?

A

Pimobendan (vetmedin)

20
Q

What is the general action of inodilators?

A

Ca sensitizer and phosphodiesterase III inhibitor

21
Q

How does calcium sensitization work?

A

Normally, troponin I inhibits actin and myosin combination until calcium binds to troponin C. Calcium sensitizers increases binding calcium to troponin C

22
Q

How does phosphodiesterase III inhibition work?

A

it prevents cAMP breakdown and increases PKA action and increases voltage-activated calcium currents

23
Q

What are the therapeutic responses to glycosides and pimobendan?

A

Increase cardiac output

Decrease in heart rate

Decrease in venous pressure

Reduced heart size

Water loss and reduced body weight

24
Q

In the heart, what does dopamine act on?

A

D5 receptors in the heart to increase cAMP

25
Q

What is dobutamine and what is it useful in treating?

A

It is a Beta-1 agonist - it is useful I/V with acute reversible heart failure

26
Q

What is amrinone and what is it useful for?

A

It is a phosphodiesterase III inhibitor useful in I/V to increase cAMP which increases Ca influx