Adrenergic Receptor Anatgonists

7/28/2019 Adrenergic Receptor Anatgonists

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2/22

Rest and Digest

Pharmacologic arithmetic: if you

administer noradrenaline +phentolamine which receptor wouldbe stimulated

a/ Beta 2

b/ Beta 1

c/alpha 2

d/ alpha 1


3/22

CVS Effects of Alpha 1 Antagonists

block vasoconstriction

fall in TPR leads to a fall in mean BP

a reflex tachycardia.


4/22

Prazosin prototype potent andvery selective alpha 1 receptor antagonists.

short acting /7 to 10 hours/

decrease in TPR

Terazosin

Intermediate duration of action, / 18 hours/

Doxazosin

long duration of action, ie 36 hours.

Adverse effects: "first dose phenomenon".

That is marked postural hypotension and fainting 30-90 minutes

after the first dose


5/22

Therapeutic Uses of Alpha Adrenergic Receptor Blockers

1/Pheochromocytoma

a tumor of the adrenal medulla or sympathetic ganglion cells.

The tumor secretes catecholamines, especially NE and epinephrine.

intermittent or sustained hypertension, headaches, palpitations, and

increased sweating.

useful in the preoperative management of patients with

pheochromocytoma


6/22

2/Hypertension

3/ treatment of peripheral vasospastic disease ie

Raynauds disease to improve perfusion

4/ Treatment of local excess concentration of a

vasoconstrictor in order to prevent necrosis.


7/22

5/ Urinary Obstruction: BPH

common in elderly men: weak stream, urinaryfrequency, and nocturia.

surgical treatments

drug therapy : Prazosin, doxazosin,

terazosin

tamsulosin/Alpha1A/

improving urine flow

partial reversal of smooth musclecontraction in the enlarged prostate and

in the bladder base.


8/22

Alpha blockers; Adverse effects

Postural hypotension Tachycardia

Sedation

Nasal stuffiness Miosis

inhibits ejaculation

E Alk l id


9/22

Ergot Alkaloids

Action Ergotamine Ergometrine

Alpha blocking + -

Direct

vasoconstriction

potent Slight

Oxytocic action Slight delayed Potent, rapid,

short DOA

CNS action ++ CTZ -

use migraine PPH


10/22

Side effects /Ergot Alkaloids

Nausea and vomiting Tingling and numbness of toes and

fingers

Gangrine Abortion

Angina pectoris


11/22


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13/22

Pharmacological ActionsBeta Blockers

13

1. CVS:

a. Heart (1): myocardial contraction HR AV-conduction & automaticity

b.BV to Sk. Muscle(2):Vasoconstriction, muscle pain & fatigue (with non- selective)

c. JG cells (1): renin release, aldosterone , angiotensin:

Na & water retention,


14/22

EYE:

IOP CNS/Neurological:

Sedation ( propranolol, carvedilol)

Respiratory: Broncho-constriction,

Metabolic:

gluconeogenesis glycogenolysis and lipolysis


15/22

Clinical applications

a. Hypertension:

b. Chronic HF: bisoprolol,

metoprolol, carvedilol

C. Glaucoma: (timolol)

diminish IOP in glaucoma by decreasing the secretion of aqueous

humor by the ciliary body.

d. Hyperthyroidism: blunting the widespread sympathetic stimulation

that occurs in hyperthyroidism


16/22

Beta-Blockers -Therapeutic Uses

Ischemic heart

disease

Arrhythmias

Neurologic diseases:

-Migraine prophylaxis: blockade of

catecholamine-induced vasodilation

in the brain vasculature

-tremor

-performance Anxiety /

stage fright/-alcohol withdrawal


17/22

Beta-Blockers - Adverse Effects

B1 blockade /cardiac/: heart failure; heart block

-bradycardia; hypotension-bradyarrhythmias

B2 blocked :Bronchocostriction; muscle fatigue

-PVD

-decreased blood flow to vital organ-Liver


18/22

Metabolic: - Increase hypoglycemic effect of

insulin(IDDM)- Increase triglycerides

- Decrease HDL

CNS; depression, nightmares

Sudden withdrawal : angina pectoris ,sudden death

- tapering the dose of the B- blocker for several weeks

before discontinuation.

R t d Di t


19/22

Rest and Digest

The diastolic BP is decreased if adrenalin

is given

a/in a large dose

b/after phentolamine

c/after atropine

d/after proranolol


20/22

es an gesThe graphs depict thechanges in BP caused by

the IV administration ofepinephrine before andafter an unknown Drug X.

Which of the followingdrugs is most likely DrugX?

A. Atropine.

B. Phenylephrine.C. Physostigmine.D. Prazosin.E. Propranolol.


21/22

A 38-yo male has recently startedmonotherapy for mild hypertension. At

his most recent office visit, he complainsof tiredness and not being able tocomplete three sets of tennis. Which oneof the following drugs is he most likely tobe taking for hypertension?

A. Albuterol.

B. Atenolol. C. Ephedrine.

D. Phentolamine.

E. Prazosin.


22/22

A 60-Yo asthmatic man comes in for acheckup and complains that he is having

some difficulty in starting to urinate.PEindicates that the man has a BPof160/100 mm Hg and a slightly enlargedprostate. Which of the followingmedications would be useful in treatingboth of these conditions?

A. Doxazosin.

B. Labetalol. C. Phentolamine.

D. Propranolol.

E. Isoproterenol.

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Adrenergic Receptor Anatgonists