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Flashcards in adrenoceptor blockers Deck (51)
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1

 All active by
 Oral route
 Parenteral route

alpha blocking drugs

2

IRREVERSIBLE LONG-ACTING

 Prototype
 Only slightly alpha1 selective
 Short elimination half life
 Long duration of action (48 hours)
 Binds covalently to the alpha receptors

PHENOXYBENZAMINE

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DoA of PHENOXYBENZAMINE

48 hours)

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REVERSIBLE SHORT-ACTING

• Prototype
• Nonselective (alpha1=alpha2)
 Duration of action
 Oral (2-4 hours)
 IV (20-40 minutes)

PHENTOLAMINE

5

ALPHA1 SELECTIVE

 Prototype
 Selective reversible alpha1 blocker
 Duration of action 8-24 hours
 Doxasozin, terazosin and tamsulosin

PRAZOSIN

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• Prototype
• Selective alpha2 competitive blockers
• Used primarily in research application

YOHIMBINE, RAUWOLSCINE

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NONSELECTIVE BLOCKERS
 Most important effects are on the ??

CVS system

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 Predictable result of the use of an agonist in a patient who has received
an alpha-blocker
 Reversal in the BP effect of large doses of epinephrine
 From pressor response (alpha receptors) to a depressor response (beta receptors)
 Not observed with phenylephrine or NE because they lack sufficient beta2 effects

EPINEPHRINE REVERSAL

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 Block alpha1 receptors much more effectively
 Cause much less tachycardia than the nonselective blockers when reducing BP

SELECTIVE ALPHA1 BLOCKERS

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• Tumor that secretes cathecolamines

pheochromocytoma

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type of BLOCKERS
• Severe hypertension caused by overdose with drugs of abuse such as amphetamine, cocaine, or phenylpropanolamine

NONSELECTIVE ALPHA

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type of BLOCKERS
 Prazosin, doxazosin, and terazosin are used in hypertension
 Used together with tamsulosin for urinary hesitancy and prevention of urinary retention with benign prostatic hyperplasia


SELECTIVE ALPHA

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Prazosin, doxazosin, and terazosin Used together with ? for urinary hesitancy and prevention of urinary retention with benign prostatic hyperplasia

tamsulosin

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• TOXICITY of alpha blockers

Main manifestation is orthostatic hypotension

15


 Competitive pharmacologic antagonists
 Propranolol is the prototype
 Developed for chronic oral use
• Bioavailability and duration of action vary widely

BETA BLOCKING DRUGS

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Beta1 receptor selectivity

Acebutolol
Atenolol
Esmolol
Metoprolol

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Advantage when treating patients with asthma

Beta1 receptor selectivity
PARTIAL AGONIST ACTIVITY

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Nonselective beta-blockers

 Nadolol
 Propranolol
 Timolol
 Pindolol

19

 Combined alpha and beta-blockers
 Optically active

Labetalol
 Carvedilol

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PARTIAL AGONIST ACTIVITY
 ”Intrinsic sympathomimetic activity”

 May be an advantage in treating patients with asthma
 At maximum dose, can cause some bronchodilatation

Pindolol
 Acebutolol
 Labetalol

21


 ”Membrane stabilizing ability”
 Disadvantage when a beta-blocker is used topically in the eye because it decreases protective reflexes and increases the risk of corneal ulceration

LOCAL ANESTHETIC ACTIVITY

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LOCAL ANESTHETIC ACTIVITY

 Acebutolol
 Labetalol
 Metoprolol
 Propranolol
 Pindolol

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• Short-acting ester
• Used only parenterally

ESMOLOL

24


4. Longest acting beta-blocker

NADOLOL

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 Less lipid soluble
 Enter the CNS to a lesser extent

ACEBUTOLOL, ATENOLOL and NADOLOL

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 EFFECTS of beta blockers in CVS

 Decrease BP
 Antagonize renin secretion
 (-) inotropic effect
 (-) chronotropic effect

27

 EFFECTS of beta blockers in RESPIRATORY

Bronchoconstriction
Increase airway resistance

28

EFFECTS of beta blockers in EYE

• Decrease intraocular pressure
• Decrease production of aqueous humor

29

EFFECTS of beta blockers inMETABOLIC AND ENDOCRINE

• Reduce insulin secretion
• Caution for insulin dependent DM

30

 CLINICAL USES of beta blockers

 Open-angle glaucoma
 Hypertension
 Angina
• Arrhythmias
• Chronic heart failure
• Pheochromocytoma

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