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ACVIM Cardiology board prep > Opie cardiovascular drugs (Beta-blockers) > Flashcards

Opie cardiovascular drugs (Beta-blockers) Flashcards

1
Q

The beta-1 receptor is part of the ____ ____ system, and is located where in the cardiac myocyte?

A

adenylyl cyclase system; located on the cardiac sarcolemma; one of the group of G protein coupled receptors

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2
Q

When activated, anenylyl cyclase produces ____ from ____

A

AC produces cyclic adenosine monophosphate (cAMP) from adenosine triphosphate (ATP)

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3
Q

The intracellular second messanger of B1-stimulation is ____

A

cAMP

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4
Q

What are the major actions (n=2) of activation of cAMP from stimulation of B1 receptors?

A

“opening” of calcium channels to increase rate and force of myocardial contraction (positive inotropic effect) and increased reuptake of cytosolic calcium into SR (relaxing/lusitropic effect)

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5
Q

In the sinus node, the pacemaker current is ___, and the rate of conduction is ___ with B1 stimulation

A

In the sinus node, the pacemaker current is increased (positive chronotropy), and the rate of conduction is accelerated (positive dromotropic effect) with B1 stimulation

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6
Q

The effect of a beta-blocking agent depends on what 4 things

A
  1. way it is absorbed
  2. binding to plasma proteins
  3. generation of metabolites
  4. extent to which it inhibits beta-receptor
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7
Q

B1-receptors are found in ___, and B2 receptors are found in ___ and ____

A

B1-receptors are found in heart muscle, and B2 receptors are found in sarcollema of bronchial and vascular smooth muscle (also found in GI tract, uterus, liver and skeletal muscle). 20-25% of B2 receptors are found in the heart (up-regulation seen in CHF)

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8
Q

B3-receptors play a role in what? Where are they primarily located?

A

Mediate vasodilation induced by nitric oxide in response to vasodilating B-blocker nebivolol; primarily located in adipose tissue and involved in regulation of lipolysis and thermogenesis

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9
Q

During B-adrenergic stimulation, the increased contractile activity resulting from greater and faster rise of cytosolic calcium is coupled to increased breakdown of ___ by the _____

A

increased breakdown of ATP by myosin adenosine triphosphatase (ATPase)

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10
Q

Increased cAMP increases phosphorylation of ___, leading to what

A

troponin-I so that interaction between myosin heads and actin ends more rapidly

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11
Q

Beta-blockers makes the heart beat slower by inhibition of ____ currents in SA node, but also has a decreased force of ____ and decreased rate of ____

A

inhibition of depolarization currents; decreased force of contraction and decreased rate of relaxation

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12
Q

Beta-1 adrenergic blockade indirectly inhibits ___ which leads to what 3 consequences

A

Calcium entrance into cell (by means of ; decreases sinus rate, rate of conduction, and contraction force

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13
Q

Where in the heart (3 locations) do beta-blockers have their effect on

A
  1. SA node (negative chronotropic-decrease HR)
  2. AV node (negative dromotropic-rate of conduction through AV node)
  3. Myocardial contraction (inotropic-contractility)
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14
Q

Beta blockage ___ contraction in smooth muscle and ___ contraction in heart muscle

A

promotes; inhibits

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15
Q

1/2 life of propanolol in dogs

A

0.77-2hr

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16
Q

Name 2 lipid-insoluble hydrophilic beta-blockers

A

sotalol and atenolol

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17
Q

Which beta blockers are excreted by the kidneys

A

sotalol and atenolol

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18
Q

Name one highly lipid-soluble beta blocker

A

propanolol

19
Q

Propanolol is mainly exreted by ___

A

liver

20
Q

Beta blockers do what to hepatic blood flow? Why is this relevant?

A

Decrease hepatic blood flow; important because blood levels of lidocaine increase leading to risk of toxicity

21
Q

What is a “first-generation” beta blocker? Name one

A

block all beta receptors (B1, B2); propanolol

22
Q

What is a “second-generation” beat blocker? Name at least 2

A

Cardioselective (b1); atenolol, metoprolol, acebutolol, bisprolol

23
Q

What is a “third-generation” beat blocker?

A

Work through 2 mechanisms:

  1. direct vasodilation possibly mediated by release of nitric oxide as for carvedilol and nebivolol
  2. alpha-adrenergic blockage as in labetalol and carvedilol
24
Q

What do beta-1 selective antagonists do to blood pressure?

A

Decrease

25
Q

Non-selective beta blockers such as propanolol may put patients at risk for what?

A

Bronchospasm

26
Q

Sotalol is a class ___ anti-arrhythmic with ___

A

Sotalol is a class III anti-arrhythmic with unique beta-blocker effects

27
Q

Carvedilol MOA

A

alpha-beta blocker with multimechanism vasodilatory properties mediated by antioxidant activity, formation of NO, stimulation of beta-arrestin-MAP-kinase and alpha-receptors

28
Q

Carvedilol may increase ___ sensitivity

A

Insulin

29
Q

Sotalol is excreted by ____

A

Kidneys; water soluble (contraindicated in patients with impaired creatinine clearance)

30
Q

What is the shortest acting beta blocker?

A

esmolol; 9 minutes

31
Q

Beta-blockers are unsafe with what disease?

A

Asthma *is this true in cats and dogs?

32
Q

List the 4 major side effects of beta-blockers

A
  1. smooth muscle spasm (bronchospasm and cold extremities)
  2. exaggeration of the cardiac therapeutic actions (bradycardia, heart block, excessive negative inotropic effect)
  3. CNS depression (insomnia, depression)
  4. adverse metabolic side effects
33
Q

Chronic beta-blockade increases ___. Furthermore, you should not ___

A

beta-receptor density; rapidly withdraw beta blockers.

34
Q

Beta blockers do what to blood sugar and insulin? Especially when used with what drug?

A

Increase blood sugar and impair insulin sensitivity especially with diuretic cotherapy; consider use of carvedilol or nebivolol

35
Q

Name the highly protein bound beta-blockers; these agents should be avoided in what clinical situation

A

propanolol, pindolol, bisprolol; avoid if plasma proteins are low

36
Q

Which beta-blocker is highly lipid soluble and readily crosses the blood-brain barrier

A

Propanolol

37
Q

Half life of atenolol

A

dogs 3.2h

cats 3.7h (duration of beta blockage effect in cats persists for 12h)

38
Q

Atenolol is high or low protein bound

A

Low (5-15%)

39
Q

Atenolol is maximally or minimally transformed in the liver; __% is excreted unchanged in urine

A

minimally; 40-50% is excreted unchanged in urine and bulk of remainder is excreted in feces unchanged (unabsorbed drug)

40
Q

Tx for emergency SVT

A

IV administration of proanolol 0.02mg/kg slowly IV up to 0.1mg/kg

OR

esmolol 0.25 to 0.5mg/kg slow IV bolus. esmolol may be administered as a CRI 50-200mcg/kg/min following initial bolus

Ca2+ channel blockers are used more frequently to tx SVT’s long term

41
Q

Patients that have been given chronic β-blocker therapy should not have the medication stopped suddenly. Why is this?

A

Chronic β-blockade results in β-receptor upregulation on the cell membrane

Acute cessation of β-blockade can result in over-stimulation of β-receptors and secondary tachycardia, etc.

42
Q

Propranolol should also be used with caution in ___ patients receiving ___, because propranolol reduces sympathetic compensation for ___

A

Propranolol should also be used with caution in diabetic patients receiving insulin, because propranolol reduces sympathetic compensation for hypoglycemia

43
Q

Sotalol can prolong the __ interval and should not be given with other medications that also prolong the __ interval (ie. __)

A

Sotalol can prolong the QT interval and should not be given with other medications that also prolong the QT interval (ie. procainamide)

44
Q

β-blockers should not be administered to patients with what electrolyte derangement? Why?

A

β-blockers should not be administered to patients with hyperkalemia, because the β-blockade reduces the potassium flux from intravascular to extravascular spaces

ACVIM Cardiology board prep (4 decks)

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