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Pharmacology > Adrenergic antagonists > Flashcards

Adrenergic antagonists Flashcards

1
Q

What is a reversible alpha antagonist?

A

Competitively inhibits the binding of physiological agonist; example: phentolamine
Graph –causes more NE needs to be added to get the same effect

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2
Q

What is an irreversible alpa antagonist

A

Covalently binds to the receptor; example: phenoxybenzamine
Inactivates the R and only way to get more R is to make new
Graph- causes a reduced max response– no matter how much NE added

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3
Q

What are the cardiovascular effects of alpha antagonists?

A

Hypotension; can cause orthostatic hypotension and reflex tachycardia. Nonspecific agents (alpha 1 and 2) are more likely to cause tachycardia

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4
Q

What happens with a high dose of epi

A

Alpha response predominates; resulting in increased blood pressure.

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5
Q

If you give an alpha antagonist prior to epinepherine

A

The effect of epinephrine at beta receptors will prevail and blood pressure will fall.

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6
Q

Why do we get rebound hypertension due to abrupt withdrawal on alpha antagonists

A

Due to upregulation of receptors, during continued administration of drug

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7
Q

What is the action of alpha-1 receptor antagonists at urethral sphincters and prostate?

A

These receptors cause contraction, so blockade can facilitate flow in patients with urinary retention.

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8
Q

Additional effects of alpha antagonists; eye

A

particularly alpha-1 (allowing parasympathetic to predominate) effects the radial muscle produces miosis

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9
Q

Additional effect of alpha antagonists; GI

A

Blockade of these receptors removes the relaxing influence of alpha receptors; causing hypermotility

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10
Q

Phenoxybenzamine

A

Non-selective, irreversible alpha blocker

  • used for hypertension resulting from Pheochromocytoma -Raynaud’s
  • adverse - tachy
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11
Q

Phentolamine

A

Non-selective alpha blocker used in hypertensive emergencies, has a short half-life
-adverse- tachy

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12
Q

Prazosin

A

Selective alpha 1 blocker

  • used in mild hypertension
  • less likely to cause tachy than phentolamine
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13
Q

Doxazosin

A

Alternatives to prazosin (alpha 1 antag) with longer half-lives
- used in BPH and mild hypertension

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14
Q

Tamsulosin

A

Selective alpha-1 blocker in prostate

-used in BPH

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15
Q

Yohimbine

A

Selective alpha-2 blocker

-used for postural hypotension and occasionally impotence

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16
Q

Pharmacokinetics of B blockers

A

Low bioavailability due to significant first pass metabolism; requiring dose titration per patient.

  • Possible high clearance due to extensive metabolism in the liver
  • polymorphisms cause some patients to be poor metabolizers leading to elevated concentrations.
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17
Q

What are the cardiovascular effects of B blockers? What happens with abrupt withdrawal

A

Bradycardia

  • decreased contractility and excitability
  • Abrupt withdrawal can cause rebound hypertension or myocardial infarction (possibly due to upregulation of receptors).
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18
Q

Renin release

A

Beta-1 stimulation causes this, therefore beta-1 blockers will suppress leading to a decrease in angiotensin; this may lower blood pressure in patients with hypertension

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19
Q

What are the cardiovascular effects of blocking B-2

A

Early rise in blood pressure (due to unopposed alpha-1 mediated vasoconstriction); can cause cold extremities (not good for Raynaud’s)

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20
Q

Contraindications: B2 and bronchoconstriction

A

Particularly in patients with asthma, contraindicated

  • beta-1 antagonist should be chosen, however receptor specificity is not complete
  • class of drugs should be avoided
21
Q

Which class of drugs should we use for glaucoma?

A

Beta blockers are among the most widely used; decrease production of aqueous humor

22
Q

What happens when we block B2 receptors?

A

Inhibits epinephrine mediated stimulation of glycogenolysis; may cause bronchospasm, blocks tremor

23
Q

What masks the symptoms of hypoglycemia in diabetes?

A

Beta blockade may block tachycardia and inhibit tremors; the primary reason these drugs are problematic in diabetic patients

24
Q

What do unopposed alpha-2 stimulation with non-specific beta blockers do on lipids?

A

Inhibit the hormone sensitive lipase; increase VLDL and decrease HDL; altering HDL/LDL ratio

25
Q

Beta blockers and membrane stabilization

A

May significantly contribute to toxicity by prolonging QRS duration and impair cardiac conduction; blocks myocyte sodium channels

26
Q

Pindolol & Acebutelol

A

Have beta agonist properties (partial agonist); weaker than catecholamines, demonstrate less bradycardia, slight vasodiation and minimal change in lipids: intrinsic sympathomimetic activity
-treats hypertension

27
Q

What are the CNS effects of B blockers?

A

Cause dizziness, fatigue, depression and sexual dysfunction; more hydrophilic drugs such as atenolol have fewer effects

28
Q

Nadolol

A

Non-selective, long lasting (24 hr) beta blocker used in hypertension and angina

29
Q

Metoprolol

A

Beta-1 selective blocker with high lipid solubility; membrane stabilizer, used widely for hypertension, angina and MI

30
Q

Esmolol

A

Very short acting beta blocker (beta-1) used for intraoperative and postoperative hypertension, arrythmias
-good for critically ill

31
Q

Labetolol

A

Non-selective for beta

  • also blocks alpha-1
  • used in severe hypertension
32
Q

Carvedilol

A

Non-selective for beta blockade; mild alpha-1 block, used in CHF and hypertension

33
Q

Guanethidine

A

Rarely used now, was used for hypertension

- acute effect is to release NE, chronic effect is to deplete NE from nerve terminals

34
Q

Resperine

A

Inhibits vesicular transport (indirect acting adrenergic antagonist) so NE cannot be taken up into vesicles
- also rarely used, causes depletion of dopamine and seratonin in the CNS leading to depression

35
Q

What are the clinical uses of B antagonists

A

Ischemic heart disease, arrhythmias, heart failure, glaucoma, hyperthyroidism, migraine, tremors; performance anxiety

36
Q

What does the B-1 blockade cause?

A

Causes decreased heart rate, stroke volume and cardiac output

  • decreased renin release
  • decreased aqueous humor production
37
Q

A BEAM

A

Beta-1 blockers: Acebutalol, Betaxolol, Esmolol, Atenolol, Metoprolol

38
Q

Please Try Not being Picky (non-selective beta blockers)

A

Propranolol, Timolol, Nadolol, Pindolol

39
Q

PAPA

A

Partial Agonist Pindolol Acebutolol

40
Q

Clinical uses for alpha blockers for urinary obstruction

A

-BPH treated with alpha 1 antag (opens up the urethra)

41
Q

alpha blockers treatment for peripheral vascular disease

A
  • Sometimes prazosin or phenoxybenzamine used to treat vasospasm in peripheral circulation (Raynauds)
  • Ca channel blockers preferred
  • Behavioral modifications preferred. Like wearing gloves outside
42
Q

Which alpha blockers would you use for chronic hypertension and what are the adverse effects?

A
  • use alpha 1 blocker (like prazosin) but usually not used alone
  • major adverse effect: orthostatic hypotension and palpitations
43
Q

What alpha blockers would you give for pheochromocytoma?

A
  • phenoxybenzamine mostly used– for several weeks before surgery to reverse chronic changes (from having incr NE circulating)
  • May need to give B blocker also– but should ONLY be given AFTER alpha block to avoid alpha-1 vasoconstriction
44
Q

What happens when you stim alpha-2 presynaptically?

A

Inh NE release

45
Q

NE effect with alpha B blocker pretreats (bp)

A

NE doesn’t stim B-2 so no vasodilation

alpha block- lowers bp

46
Q

Epi response with alpha and beta block pretreats (bp)

A

alpha- decr bp

beta- incr bp

47
Q

Isoproterenol effect with alpha and beta block pretreats (bp)

A
  • isoproterenol is beta agonist
  • alpha- no effect
  • beta- less of a decr in bp
48
Q

Terazosin

A

Alternatives to prazosin (alpha 1 antag) with longer half-lives
- used in BPH and mild hypertension

Pharmacology (10 decks)

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