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Pharmacology II > Cardiac drugs : decrease afterload & alter contractility > Flashcards

Cardiac drugs : decrease afterload & alter contractility Flashcards

1
Q

Indications for cardiac drugs that decrease afterload

A
  • mitral valve regurgitation
  • cardiomyopathy
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2
Q

How can afterload be decreased directly?

A

arterial dilator

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3
Q

How can afterload be decreased indirectly?

A

decrease ventricular volume

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4
Q

What is Hydralazine

A
  • arterial vasodilator
  • manage mitral valve regurgitation
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5
Q

What is usually administered concurrently with Hydralazine?

A

negative chronotropic drug due to reflex tachycardia

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6
Q

Common adverse effect of Hydralazine

A

hypotension

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7
Q

How does Phosphodiesterase inhibitor decrease afterload?

A

indirectly increase effects of nitric oxide by inhibiting breakdown of cGMP

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8
Q

What vessel does phosphodiesterase inhibitor affect?

A

pulmonary arteries in dogs

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9
Q

What is mechanism of action for Amlodipine?

A

Ca2+ channel block vasodilator
- decrease intracellular Ca2+
- decrease smooth muscle contraction
- minimal cardiac effect due to low affinity

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10
Q

Indication for Amlodipine

A

cats with systemic hypertension
dogs with hypertension & refractory congestive heart failure

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11
Q

How does prazosin decrease afterload?

A
  • selective alpha 1 receptor blocker
  • relaxes smooth muscle in both arteries & veins
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12
Q

How does beta blocker decrease afterload?

A
  • decrease sympathetic tone
  • decrease cardiac contractility
  • decrease renin release from kidneys
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13
Q

What are positive inotropic drugs used for?

A

increase cardiac contractility
treat cardiomyopathy

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14
Q

General characteristics of Pimobendan

A
  • inodilator
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15
Q

Mechanism of action of pimobendan to increase contractility

A
  1. inhibition of phosphodiesterase 3 & increase intracellular cAMP
    - increase contractility & improve muscle relaxation
  2. Ca2+ sensitizer
    - minimize increase of O2 demand
  3. arteriole dilation
    - lower vascular resistance
    - inhibition of phosphodiesterase 3 & 5
    - increase cAMP & cGMP in peripheral blood vessels
  4. neurohumoral balance
    - redcuce sympathetic imbalance
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16
Q

Indication of Pimobendan

A

cardiomyopathy & mitral valve regurgitation

17
Q

Adverse effects of pimobendan

A

decreased appetite, lethargy, diarrhea, dyspnea

18
Q

Mechanism of action of Digoxin

A
  1. inhibition of Na/K ATPase
    - increase intracellular Na
    - trigger Na/Ca exchange
    - increase Ca release from SR
  2. increase vagal tone
    - decrease HR
19
Q

Adverse effects of Digoxin

A

GI: anorexia, vomiting, diarrhea
Cardiac: tachyarrhythmia/ bradyarrhythmia, AV block

20
Q

Electrolyte interaction of Digoxin

A
  • hyperkalemia: reduce effectiveness
  • hypokalemia: facilitate mechanism ( potentially cause toxicosis
  • hypercalcemia can cause toxicosis (Ca2+ influx into myocardial cells)
21
Q

Drug interactions of Digoxin

A
  • Quinidine : displace digoxin from tissue binding sites
  • Furosemide: decrease clearance
  • spironolactone: increase K; less effective
22
Q

Treatment for Digoxin toxicity

A
  • decrease/ stop digoxin
  • administer antiarrhythmics
  • administer K+
  • anti-digoxin antibody
23
Q

Mechanism of action of Dobutamine

A

Stimulation of beta 1 receptor
- increase heart contractility
- increase release ca2+ from the intracellular storage
- does not increase HR

24
Q

Why can’t Dobutamine be used for long-term management of cardiomyopathy?

A

down-regulation of beta1 receptor over time

25
Q

How are dobutamine administered?

A

CRI due to short half life

26
Q

Adverse effect of dobutamine

A
  • tachycardia & ventricular arrhythmia with high dose
  • can cause seizure at low infusion rates in cats
27
Q

Drug reaction of Dobutamine

A

incompatible with alkaline fluid & bicarbonate

28
Q

What are Dopamine used for?

A
  • correct hypotension when there is no response to fluid volume replacement
  • short-term management of congestive heart failure
29
Q

What does Dopamine bind at low dose?

A

dopamine receptor ( vasodilation)

30
Q

What does dopamine bind at medium dose?

A

beta 1 receptor ( cardiac stimulation)

31
Q

What does dopamine bind at high dose?

A

alpha receptor (vasoconstriction)

32
Q

Adverse effects of Dopamine

A

excessive vasoconstriction in the kidn eys

33
Q

What are the indications for negative inotropic drugs?

A

hypertrophic cardiomyopathy

Pharmacology II (8 decks)

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