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VET 408: Cardio/Respiratory > CHF Pharmacology > Flashcards

CHF Pharmacology Flashcards

1
Q

what are the three main categories of drugs to treat congestive heart failure

A
  1. diuretics
  2. vasodilators
  3. positive inotropes
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2
Q

what drug classes reduce preload

A

diuretics
venodilators

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3
Q

what drug class reduces afterload and MVO2

A

arteriodilators

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4
Q

what are the common drugs used to treat heart failure in dogs

A

furosemide (lasix)
pimobendan
ACE inhibitors
spironolactone

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5
Q

what are the common drugs used to treat heart failure in cats

A

furosemide
clopidogrel
ACE inhibitors

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6
Q

what drug class should ALL CHF treatment include

A

diuretics

preferably loop diuretics

can be used in emergency and at home

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7
Q

general mechanism of diuretics

A

prevents the reabsorption of Na, Cl, and H2O

increases water excretion to decrease plasma volume (decreases venous pressure, preload)

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8
Q

mechanism of action of loop diuretics

A

inhibits Na/K/2Cl exchanger in thick ascending loop of henle

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9
Q

loop diuretics examples

A
  1. furosemide (lasix)
  2. torsemide
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10
Q

what is required in order to treat with furosemide

A

healthy kidney - must be actively secreted into tubule lumen

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11
Q

use of furosemide vs torsemide

A

furosemide - rapid onset, short duration of action

torsemide - slower onset, long duration of action (chronic management of advanced CHF)

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12
Q

mechanism of action of thiazide diuretics

A

inhibits Na/Cl co-transporter in the DCT

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13
Q

example of thiazide diuretic

A

hydrochlorothiazide (HCTZ)

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14
Q

use of HCTZ

A

used in conjunction with loop diuretic (furosemide) to increase the potency by extending Na/water excretion to the DCT

can cause additional ion loss but increases Ca retention

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15
Q

mechanism of action of potassium sparing diuretics

A

blocks the action of aldosterone in the collecting ducts

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16
Q

example of a potassium sparing diuretic

A

spironolactone

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17
Q

use of spironolactone

A

blocks the activity of Na/K ATPase to reduce Na reabsorption and K excretion

weak diuretic - used in conjunction with furosemide

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18
Q

what do venodilators decrease

A

preload

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19
Q

what do arteriodilators decrease

A

afterload (by decreasing regurgitant fraction)

20
Q

regurgitant fraction

A

percentage of blood in the LV that regurgitates back into the LA

21
Q

categories of vasodilators

A
  1. direct acting
  2. Ca channel blockers
  3. RAAS inhibitors
  4. sympatholytic agents
  5. phosphodiesterase inhibitors
22
Q

mechanism and example of direct acting vasodilators

A

relax smooth muscle without blocking constrictor mechanisms

sodium nitroprusside

23
Q

mechanism and example of Ca channel blockers

A

decrease Ca influx into smooth muscle

amlodipine, clevidipine

24
Q

mechanism and example of RAAS inhibitors

A

block production or effect of ANG II

ACE inhibitors, ANGII receptor blockers (ARBs)

25
Q

mechanism of sympatholytic agents

A

block alpha receptors

26
Q

mechanism and example of phosphodiesterase inhibitors

A

increase cAMP to cause smooth muscle relaxation; also causes cardiac muscle contraction

pimobendan

27
Q

why is blocking the RAAS cascade used to treat CHF

A

RAAS gets overstimulated in CHF

ANG II + aldosterone cause excess vasoconstriction and Na/H2O reabsorption, leading to cardiac hypertrophy/fibrosis/remodeling

decreasing RAAS will reduce the adverse effects

28
Q

mechanism of ACE inhibitors

A

block the conversion of ANG I to ANG II

requires activation by hepatic metabolism

29
Q

ACE inhibitor examples

A

enalapril, benazepril

30
Q

side effect of ACE inhibitors

A

dilates afferent arteriole resulting in decreased glomerular pressure

causes GFR to decrease and creat/BUN to accumulate leading to acute azotemia

kidney will accommodate if animal does well through initial azotemia

31
Q

amlodipine vs clevidipine uses

A

amlodipine: treats systemic hypertension by reducing afterload; can be used even if patient with MV disease is not hypertensive

clevidipine: IV administration; used in ER as a CRI

32
Q

sodium nitroprusside uses

A

ER treatment of life threatening pulmonary edema or systemic hypertension in dogs by decreasing LV afterload (reduces MVO2 and regurgitation)

myxomatous MV disease more common use than DCM

33
Q

mechanism of action of positive inotropes

A

increases intracellular Ca availability OR sensitivity to Ca

34
Q

examples of positive inotropes

A

pimobendan
digoxin
dobutamine

35
Q

pimobendan mechanism

A

PDE inhibitor; prevents degradation of cAMP to increase signaling in cardiac cells AND sensitizes the contractile apparatus to Ca

ALSO works in vascular smooth muscle to increase cAMP leading to dilation

36
Q

why is pimobendan considered an “inodilator”

A

increases inotropy in the heart AND relaxes vascular smooth muscle (dilation)

37
Q

why does pimobendan have a lower risk of Ca induced arrhythmias than other positive inotropes

A

because it does not increase intracellular Ca

increases cAMP signaling and increases sensitivity to Ca

38
Q

digoxin mechanism

A

inhibits Na/K ATPase to activate Na/Ca exchanger and increase Ca influx resulting in positive inotropy

39
Q

how does digoxin affect baroreceptors

A

increases vagal tone and decreases sympathetic input

40
Q

what is the main use of digoxin

A

decrease heart rate during atrial fibrillation

can be used for concurrent CHF and atrial fibrillation

41
Q

mechanism of dobutamine

A

catecholamine; stimulates B1 receptors and increases cAMP to increase Ca influx

B1 selective but also has minor B2 and a1/2 effects

allows for positive inotropy with minimal vasoconstriction (no net effect on BP)

42
Q

use of dobutamine

A

used in ER for treatment of cardiogenic shock

less used than pimobendan because it increases workload on the heart

43
Q

what species requires anti platelet therapy included in treatment of CHF

A

cats - highly predisposed to thrombosis during heart failure (Virchow’s triangle)

44
Q

what anti platelet therapy is most commonly used

A

clopidogrel

45
Q

clopidogrel mechanism

A

decreases platelet stickiness

VET 408: Cardio/Respiratory (38 decks)

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