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1. Pharmacology > Cardiac Pharmacology > Flashcards

Cardiac Pharmacology Flashcards

1
Q

Goals of pharmocologic therapy of CHF

A

Improves quality of life, prognosis, and contractile function*

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2
Q

Drugs used to DECREASE cardiac load

A

Diuretics (↓blood volume)
Vasodilators (↓ preload and afterload)

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3
Q

Drugs used to INCREASE cardiac pumping efficiency

A

Catecholamines
Phosphodiesterase inhibitors
Cardiac glycosides
Calcium sensitizers

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4
Q

Why is calcium activation a problem?

A

Ca2+ release requires more O2/ energy

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5
Q

Cardiac activation

A
  1. Sensitizes muscle to the Ca2+ (↑contraction, doesn’t require O2)
  2. ↑ contractility by ↓ Ca2+ uptake (keeping Ca+ longer)
  3. Causes more Ca2+ to come in and release more Ca2+
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6
Q

Calcium-tension relation

A

Too much Ca2+ in and out of the cell = overload
Causes ↓ heart response to Ca2+ and arrhythmias

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7
Q

Catecholamines

A

B agonists
Stimulation of b1 receptors has both inotropic and chronotropic effects

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8
Q

What does persistant stimulation of B1 receptors by agonists do?

A

Produces receptor down regulation and rapid ↓ in drug effectiveness (tolerance)
SHORT-TERM DRUGS

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9
Q

Catecholamine drugs

A

Dobutamine and dopamine

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10
Q

Dobutamine

A

↓ output failure patients (CHF patients)
Inotropic effects without vasoconstrictive activity (b1)
Vasodilation (b2)
Only available IV (CRI)

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11
Q

Dopamine

A

Not for CHF patients, for shock patients
IV administration only!
Metabolized in kidney, liver by monoamine oxidase (MAO) and COMT

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12
Q

Cardiac Glycosides (digitalis)

A

From foxglove
Used in the treatment of dropsy (edema), congestive heart failure, dysrhythmias
Positive inotropic effect

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13
Q

Why don’t vets like to use digitalis glycosides?

A

Narrow TI
↑ toxicity range

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14
Q

Cardiac Glycoside drug

A

Digoxin

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15
Q

Digoxin

A

Most common digitalis
Renally excreted and blood levels rise with ↓ GFR (lower dose if patients has renal insufficiency)

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16
Q

Digitalis MOA

A
  1. Inhibits K+ on Na+, K+-ATPase
  2. Intracellular Na+ ↑
  3. Na+-Ca++ exchanger : pumps Ca++ in, Na++ out
  4. Intracellular Ca++ accumulates and complexes with tropinin → contraction
  5. Effects cardiac and smooth muscles
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16
Q

Digitalization effects

A

↑ excitability, refractory pd.
Delayed afterdepolarization
↓ conduction velocity (vagal effects), automaticity
Tachyarrhythmias
Heart block with high doses

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17
Q

Digitalis dosing

A

Emergency situation: loading dose
Non- emergency: slow administration with maintenance dosing

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18
Q

Calcium sensitization

A

Drugs that ↑ myofilament responsiveness to given Ca
No Ca2+ overload

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19
Q

Pimobendan (Vetmedin)

A

Positive inotropic and vasodilator effects
Smaller cardiac preload and afterload
MV disease in dogs

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20
Q

Pimobendan MOA

A

Ca2+ sensitizer and inhibits PDE 3
Peak concentration @ 4 hours, cardio effects 2-4 hrs

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21
Q

Drugs that ↓ cardiac workload

A

Cause fluid and Na retention in vessels (compensates for ↓ pumping ability)
Excessive retention: overload, pulmonary edema, deoxygenation of blood, peripheral edema
Vasodilators and ACE inhibitors

22
Q

Vasodilators

A

Unloads the failing heart
↓ workload = ↓ arterial pressure so left ventricle pumping blood with lower resistance

23
Q

Arterial vasodilation

A

Reduction in afterload
Side effects: hypotension, reflex tachycardia
Not used in patients with late stage heart failure, SBP <70

24
Q

Arterial vasodilators

A

Amlodipine (Norvasc)
Hydralazine

25
Q

Amlodipine (Norvsac)

A

1-4 dihydropyrodine
Peripheral calcium channels blockers with little central effects
Enhances NO-

26
Q

Hydralazine

A

Research/ emergency drug
↓ systemic vascular resistance in heart failure
Side effects: reflexive tachycardia, hypotension, GI distress

27
Q

T/F: hydralazine has an unknown MOA

A

TRUE

28
Q

Venodilators

A

↑ venous capacity reduces preload and relieves congestion
Ex: nitroglycerin

29
Q

Nitroglycerin

A

Cats with fluid buildup
2% ointment (gloves) on hairless area
Rapidly develops tolerance (once a day)

30
Q

Mixed (balance) dilators

A

Sodium nitroprusside: prototype for acute left CHF, must use saline
Adverse effects: cyanide toxicity, not useful in 2-3 days

31
Q

With nitroprusside you should avoid _______

A

Extravasation (bad wound if not in vessel)

32
Q

Drug tolerance

A

Depletion of sulfhydryl group
Inactive aldehyde dehydrogenasde
Production of peroxynitrite (blocks GTP-cGMP conversion)

33
Q

ACE inhibitors

A

Inhibits angiotensin converting enzyme (ACE) → prevents angiotensin 2 formation → prevents vasoconstriction
Used for CHF

34
Q

Adverse effects of ACE inhibitors

A

Possible renal insufficiency

35
Q

ACE inhibitor drugs

A

Enalapril and benzepril

36
Q

Enalapril

A

Prodrug that undergoes hepatic hydrolysis forming enalaprilat
Distributed in all tissues except CNS, cross placenta, enter milk in traces

37
Q

Enalapril toxicity is @ ___________

A

200 mg/ kg

38
Q

Benazepril (prodrug)

A

Rapidly metabolized to benazeprilat
Eliminated via hepatic metabolism

39
Q

Angiotensin Receptor Blockes (ARBs)

A

Antagonizes angiotensin 2 binding to AT1 subtype receptor in smooth muscle and adrenal gland
Used more for hypertensive cats
Drugs that end in “Sartan”

40
Q

Temisartan

A

Only approved drug in vet med
Selectively binds to AT1 subtype receptors
Doesn’t metabolize well in dogs

41
Q

ARB excretion

A

Biliary elimination into the feces (86%-100%)

42
Q

Prazosin HCL

A

A1 adrenergic antagonist
Mixed arterial and venous dilation
Hepatic metobolism

43
Q

Prazosin interactions

A

Displaced by high protein bound drugs like sulfonamides and warfarin

44
Q

What is significant about loop Acting Diuretics

A

Only drug that’ll save a patient in respiratory distress due to cardiogenic edema
High ceiling

45
Q

Loop acting diuretics

A

Secreted into the tubular lumen
Inhibits Na+, K+, CL- in thick ascending loop of henle
Ex: Furosemid (Lasix) and Torsemide (demadex)

46
Q

Fursosemid (lasix)

A

Venodilation occurs with IV administration
Dehydration and hypokalmeia common side-effects + metabolic alkalosis

47
Q

TORESEMIDE

A

Used when level D heart failure
Longer duration of action than furosemide
Side effects ↑BUN and creatinine, ↓ collagen and myocardial fibrosis

48
Q

Thiazide Diuretics

A

Directly inhibits Na+ CL-/ H2O cotransporter in DCT
Synergist drug
Low ceiling, given 2nd
Induce dehydration and hypokalemia

49
Q

Examples of thiazide

A

Hydrocholorothiazide (pure) and chlorthiazide (capsule)

50
Q

Potassium Sparing Diuretics

A

Used in early heart failure for antifibrotic effect because weak
Given in combo with other drugs
Reduce loss of K+ from other drug

51
Q

Potassium Sparing Diuretic drugs

A

Spironolactone → Canrenone

52
Q

Potassium Sparing Diuretics MOA

A

Inhibits Na/H2O resorption in DCT/CT
Antifibrotic properties

1. Pharmacology (29 decks)

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