Flashcards in adrenoceptor blockers Deck (51):
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
3
DoA of PHENOXYBENZAMINE
48 hours)
4
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
6
• Prototype
• Selective alpha2 competitive blockers
• Used primarily in research application
YOHIMBINE, RAUWOLSCINE
7
NONSELECTIVE BLOCKERS
Most important effects are on the ??
CVS system
8
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
9
Block alpha1 receptors much more effectively
Cause much less tachycardia than the nonselective blockers when reducing BP
SELECTIVE ALPHA1 BLOCKERS
10
• Tumor that secretes cathecolamines
pheochromocytoma
11
type of BLOCKERS
• Severe hypertension caused by overdose with drugs of abuse such as amphetamine, cocaine, or phenylpropanolamine
NONSELECTIVE ALPHA
12
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
13
Prazosin, doxazosin, and terazosin Used together with ? for urinary hesitancy and prevention of urinary retention with benign prostatic hyperplasia
tamsulosin
14
• 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
16
Beta1 receptor selectivity
Acebutolol
Atenolol
Esmolol
Metoprolol
17
Advantage when treating patients with asthma
Beta1 receptor selectivity
PARTIAL AGONIST ACTIVITY
18
Nonselective beta-blockers
Nadolol
Propranolol
Timolol
Pindolol
19
Combined alpha and beta-blockers
Optically active
Labetalol
Carvedilol
20
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
22
LOCAL ANESTHETIC ACTIVITY
Acebutolol
Labetalol
Metoprolol
Propranolol
Pindolol
23
• Short-acting ester
• Used only parenterally
ESMOLOL
24
4. Longest acting beta-blocker
NADOLOL
25
Less lipid soluble
Enter the CNS to a lesser extent
ACEBUTOLOL, ATENOLOL and NADOLOL
26
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
31
TOXICITY in CVS
1. CVS
1. Bradycardia
2. AV blockade
3. Heart failure
32
TOXICITY in RESPIRATORY
1. Worsen the asthma
33
TOXICITY in CNS
1. Sedation
2. Fatigue
3. Sleep alteration
4. Depression
5. Psychosis
34
TOXICITY in CNS
1. Sedation
2. Fatigue
3. Sleep alteration
4. Depression
5. Psychosis
35
Conversion of the pressor response to epinephrine (typical of large doses) to a blood
pressure–lowering effect; caused by α blockers, which unmask the β2 effects of epinephrine
Epinephrine reversal
36
Partial agonist action by adrenoceptor blockers; typical of several β blockers (eg, pindolol,
acebutolol)
Intrinsic sympathomimetic
activity (ISA)
37
Local anesthetic action; typical of several β blockers (eg, propranolol)
Membrane-stabilizing
activity (MSA)
38
Hypotension that is most marked in the upright position; caused by venous pooling (typical of α blockade) or inadequate blood volume (caused by blood loss or excessive diuresis)
Orthostatic hypotension
39
A tumor consisting of cells that release varying amounts of norepinephrine and epinephrine
into the circulation
Pheochromocytoma
40
Drugs used in glaucoma.
Beta blockers
Timolol, others
41
Drugs used in glaucoma
Prostaglandins
Latanoprost, others
42
Drugs used in glaucoma.
Cholinomimetics
Pilocarpine, physostigmine
43
Drugs used in glaucoma.
Alpha agonists
Nonselective:
epinephrine
44
Drugs used in glaucoma.
Alpha2-selective agonists
Apraclonidine, brimonidine
45
Drugs used in glaucoma.
Carbonic anhydrase inhibitors
Acetazolamide, dorzolamide
46
Drugs used in glaucoma.
Osmotic agents
Mannitol
47
Clinical Applications
Pheochromocytoma, antidote to overdoseof α agonists
Phentolamine
48
Clinical Applications
Pheochromocytoma,
carcinoid, mastocytosis, Raynaud’s
phenomenon
phenoxybenzamine
49
Clinical Applications
Hypertension, benign
prostatic hyperplasia
PRAZOSIN
50
Clinical Applications
Obsolete use for
erectile dysfunction •
research use
YOHIMBINE
51