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Drugs competitively
block adrenergicreceptors
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Relative affinity for 1and / or 2 receptors
Some of them have 'Intrinsicsympathomimeticactivity ISA
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Some have membranestabilizing effect ( LA orquinidine like effect )
Some have high lipid
solubility; with centraldepressant effect
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B-blockers
Non selectivePropranolol
Pindolol
Selective 1
Atenolol
Metoprolol
Combined & blocker
labetalol &carvedilol
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B-blockers
Lipophilic Hydrophilic
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Lipophylic Hydrophilic
oralabsorption
Complete Irregular
Livermetabolism
Yes No
T 1/2 Short Long
CNS side
effects
High low
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HydrophilicLipophylic
AtenololPropranolol
AcebutalolTimolol
Labetalol
Carvedilol
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The prototype of betablockers.
It has equal affinity for 1& 2
It has NO ISA . It possess local anesthetic
action
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Heart- ve chronotropic ,
- ve inotropic- ve dromotropic
COP, work & O2 consumption. automatcity & excitability
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vasoconstriction
( B2blocking) blood supply toorgans
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1. COP (1- blocking effect).2. Block rennin release, so Ag II &
aldosteron (1- effect).
3. NE release from Nerveterminals.
4. central sympathetic outflow.5.Ressetting of baroreceptor
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Bronchoconstriction in
susceptible patients(2- blocking effect).
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1. Hypoglycemia due todecrease both
glycogenolysis & glucagonsecretion
2. Inhibit lipolysis
3. Sodium retention : BP in renal perfusion Na+retention& plasma volume.
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Propranolol depresses
CNS reduce tremors
due to anxiety
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1.Hypertension.
2. Angina pectoris
3. Cardiac arrhythmia.
4. Myocardial infarction
5. Hyperthyrodism
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6. Open-angle Glaucoma(chronic): Timolol
7. Prophylaxis of Migraine
headache
8. Management of familial
tremors & anxiety9. Pheochromocytoma with
-blockers (never alone)
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1-Block of cardiac 1
-receptors:
-ve inotropic heart failure(treated by digitalis).
-ve chronotropic bradycardia(Treated by atropine).
-ve dromotropic heart failure.Hypotension.
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2. Blockade of2:Bronchospasm and asthma.
Hypoglycemia (symptomless
hypoglycemic coma).
Vasoconstriction (cold
extremities).Coronary vasoconstriction.
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Exacerbates angina,
tachycardia, maylead to arrhythmias
Rebound hypertension.
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Bronchial asthma.
Type I diabetes mellitus.
Peripheral vascular disease.
Heart block, severe HF,
massive MI.
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PharmacokineticInteractions
PharmacodynamicInteractions
1. Hepatic enzyme
inhibitors as:cimetidine & isoniazid
1. Anti-diabetic drugs
e.g. insulin.
2. Hepatic enzyme
inducers as:
barbiturates,
phenytoin, & rifampin
2. Verapamil (calcium
channel blocker)
3. Non-steroidal anti-
inflammatory drugs
Drug interactions
Drugs Selectivity PA LA activity Lipid T (h)
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Drugs Selectivity PAactivity
LA activity Lipidsolubility
T (h)
Propranolol 1 , 2 - + High 4-6
Pindolol 1 , 2 + Weak Moderate 3-4
Atenolol 1 - - Low 6-9
Acebutalol 1 + + Low 3-4
Labetalol 1, 1 + + Moderate 5
Carvedilol 1 ,
1 - - Moderate 6-8
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