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Pharmacology > Adrenergic Receptor Antagonists > Flashcards

Adrenergic Receptor Antagonists Flashcards

1
Q

Name some cardiovascular effects of antagonizing the alpha1 receptor.

A
  1. Decreased PVR
  2. Lowered BP
  3. Postural hypotension due to failure of venous vasoconstriction upon standing

(Remember alpha 1 is really important for venoconstriction and vascular tone for maintaining changes in tone with position changes etc. If we block it we are blocking compensation for these types of changes)

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2
Q

Name some cardiovascular effects of antagonizing the alpha 2 receptor.

A
  1. Increases NE release from nerve terminals (we are blocking that negative feedback mechanism).

Remember: you can end up with increased circulating NE so if we block the alpha receptor and not the beta NE could end up stimulating the B1 receptor and cause tachycardia.

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3
Q

What kind of effects does antagonizing the alpha receptors have the GU system, eyes and nose?

A
  1. GU- blockade in the prostate and bladder cause MUSCLE RELAXATION and EASE micturation (used in BPH for this effect)
  2. Eyes: Miosis: contracted pupil
  3. Nose: increased nasal congestion (side effect).
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4
Q

What kind of antagonism is possible with alpha antagonists?

A

Either competitive antagonism or covalent antagonism.

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5
Q

At what receptor does Phentolamine work? What does it result in?

A
  1. It is NON-selective alpha blocker.
  2. Vasodilation, decreased BP, increased HR and increased CO.

*Increased HR is because of the blocked negative feedback and baroreceptors which make this reflexive tachycardia a bit more dramatic.

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6
Q

When is Phentolamine used? Dose? Onset? DOA? Elimination 1/2 time?

A
  1. Used in hypertensive emergencies (pheocromocytoma or autonomic dysreflexia) where the dose is 30-70 mcg/kg IV with an onset of 2 minutes and a DOA of 10-15 minutes. Elimination half time is 19 minutes which makes this drug EXCELLENT to control on a short term basis.
  2. Used in local infiltration for accidental extravascular administration of sympathomimetics, 2.5-5.0MG in 10ml (infiltrate in the area to combat constriction).
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7
Q

Why must we pay special attention to phenoxybenzamine? What kind of selectivity does it have?

A
  1. Because it binds covalently so you are STUCK with it.

2. A little more selective for alpha one than alpha 2

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8
Q

What kind of action does phenoxybenazmine have?

A

It decreases SVR, vasodilation.

*Some HR increases but not as much as phentolamine but we do still have the baroreceptors contributing and a little hit on alpha 2.

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9
Q

What kind of drug is phenoxybenzamine? Onest? Half-time? When is it used?

A
  1. Pro-drug (liver metabolizes)
  2. 1 hour onset time
  3. Long acting E1/2t : 24 hours
  4. Pre-op pheoxchromocytoma and Raynaud’s
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10
Q

What kind of effect do beta-adrenergic receptor antagonists have on the heart?

A
  1. Improve O2 supply and demand balance (decrease HR)
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11
Q

What kind of effect can beta-adrenergic receptors antagonists have on the airway?

A
  1. Can provoke bronchospasm.
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12
Q

What kind of effect do the beta-adrenergic receptor antagonists have on the juxtaglomerular cells?

A
  1. Decrease renin release (an indirect way of decreasing BP)
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13
Q

What kind of effect do the beta-adrenergic receptor antagonists have on the pancreas?

A
  1. Decreased stimulation of insulin release by epi at B2

2. Masked symptoms of hypoglycemia at B1

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14
Q

What kind of effect do the beta-adrenergic receptor antagonists have on the blood vessels?

A
  1. Vasoconstriction in skeletal muscles, PVD symptoms increased (SE = decreased excercise tolerance).
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15
Q

Name the three MOAs of the beta-adrenergic receptor antagonists.

A
  1. Selective binding to beta receptors
  2. Competitive and reversible inhibition
  3. Chronic use is associated with increase in the number of receptors.
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16
Q

Beta-adrenergic receptor antagonists are derivatives of what drug?

A

Isoproterenol

17
Q

Large doses of cardioselective beta blockers….?

A

Lose their selectivity.

18
Q

What kind of agonist is Metoprolol? What is it’s selectivity related to? What two things does it decrease?

A
  1. Selective B1 blocker
  2. Selectivity is dose related
  3. Decreases inotropy and chronotropy
19
Q

How much of Metoprolol goes through the first pass effect? Dose PO? Dose IV? E1/2T?

A
  1. 60%
  2. PO 50-400mg
  3. 1-15mg
  4. 3-4 hours.
20
Q

Which drug is the most selective beta-1 antagonist? When is it very useful

A

Atenolol, in cardiac patients with CAD.

21
Q

What is the E1/2t of atenolol? When is it increased?

A
  1. 6-7 hours

2. renal disease

22
Q

Esmolol works at which receptor? Onset? DOA? Typical Dose? E1/2t?

A
  1. Selective B1 antagonist
  2. Rapid onset
  3. Short acting DOA under 15 minutes
  4. Typical dose of 0.5mg/kg IV or (10-180mgIV) can start an infusion of 50-200mcg/kg.min
  5. 9 minutes
23
Q

Esmolol affects heart rate without affecting what?

A

without decreasing blood pressure significantly. In doses uses, it does not occupy sufficient beta receptors to cause negative inotropy.

24
Q

What is esmolol rapidly hydrolyzed by?

A

Plasma esterases, but not the same ones responsible for the metabolism of succhs.

25
Q

What kind of side effects do we see with B blockers?

A
  1. CV system (b1) decrease Hr, Contractility and BP
  2. Exacerbation of PVD (block of beta 2 vasodilation)
  3. Airway resistance bronchospasm
  4. Metabolism- alter carb and fat metabolism, mask hypoglycemic increase in HR
  5. Distribution of extracellular potassium- inhibit uptake of potassium into skeletal muscles (B2)
  6. Interaction with anesthetics- may have decreased BP with IAs
  7. Nervous system- fatigue, lethergy
  8. N/V/D
26
Q

What are four relative contraindications of beta blockers?

A
  1. Pre-existing AV heart block or acute cardiac failure.
  2. Reactive airway disease
  3. DM (need to be really really really advised about hypoglycemia and strict BS monitoring)
  4. Hypovolemia.
27
Q

Name 6 clinical uses of B-blockers.

A

HTN, Management of Angina, Decrease mortality in treatment of post MI patients, used periop and preop for patients at risk for MI, suppression of tachyarrythmias, prevention of excessive SNS activity.

28
Q

Which drug is a combined alpha and beta blocker? Which receptors?

A
  1. Labetalol

2. Selective at alpha one, beta 1 and 2 receptors. The IV Beta : Alpha blockade is 7:1.

29
Q

How is labetalol metabolized? What is its’ E1/2t? When is it prolonged?

A
  1. Conjugation of glucuronic acid <5% in the urine.
  2. 5-8 hours.
  3. Liver disease
30
Q

What kind of CV effects do we see from labetalol?

A

Decreased BP, SVR, HR and CO

31
Q

When is the maximum drop in BP seen with IV labetaolol?

A

5-10 minutes after (don’t be inpatient)

32
Q

What is the dose of Labetalol?

A

0.1-0.5 mg/kg (usually 5mg at a time for mild hypertension in the OR)

33
Q

What side effects can we see with labetalol?

A

OHTN (because of that mild A1 blockade), Bronchospasm, HB, CHF, bradycardia

Pharmacology (23 decks)

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