Adrenoceptor Agonist

Question 1

Adrenoceptor agonist

Answer 1

• useful in many clinical conditions
• drugs affinity will determine their effect
• classified as either alpha or beta

Question 2

Alpha 1 receptors

Answer 2

• postynaptic smooth muscle, exocrine glands, and CNS
• contraction of vascular smooth muscle (increase BP), iris dilator muscle (mydriasis), smooth muscle in lower urinary tract (bladder, urethra, and prostate)

Question 3

Alpha 2 receptors

Answer 3

• presynaptic nerve endings
• causes feedback inhibition to prevent further release of NE
• also found on platelets, intestinal, hepatic,, renal, endocrine tissue, ocular, adipose

Question 4

Beta 1 receptors

Answer 4

• produce cardiac stimulation
• increase HR
• increase contractility
• increase cardiac impulse conduction
• increase renin secretion

Question 5

Beta 2 receptors

Answer 5

• mediate relaxation of bronchial, uterine, and vascular smooth muscle
• skeletal muscle (increase glucose in blood)

Question 6

Beta 3 receptors

Answer 6

-promote lipolysis

Question 7

Dopamine receptor

Answer 7

• activated by dopamine only
• D1 receptors mediate vascular smooth muscle relaxation
• D2 receptors modulating neurotransmitter release
• Fenoldopam is D1 receptor agonist

Question 8

Imidazoline receptor

Answer 8

• activated by adrenoceptor agonist and substances containing imidazoline structures
• found in CNS
• Clonidine: activates both alpha 2 and imidazoline to decrease BP

Question 9

Classification of adrenoceptor agonist

Answer 9

• direct acting agonist
• indirect acting agonist
• mixed acting agonist

Question 10

Direct acting agonist

Answer 10

• bind to and activate adrenoceptors
• cateholamines: epi, NE, dopamine, isoproterenol, dobutamine
• noncatecholamines: albuterol, clonidine, midodrine, oxymetazoline, phenylephrine, terbutaline
• catecholamines are broke down quickly
• noncatecholamines have longer DOA

Question 11

Epinephrine

Answer 11

• adrenergic agonist
• low dose: beta effects on vascular system
• high dose: alpha effects are strongest
• clinical uses: bronchospasm, glaucoma, anaphylactic shock, in anethestics

Question 12

Norepinephrine

Answer 12

• adrenergic receptors
• alpha adrenergic is most effected more than beta
• vasoconstriction and increase BP

Question 13

Isoproterenol

Answer 13

• strong beta 1 and 2 receptor agonist with little alpha effect
• increases HR
• no blood vessel constriction so no increased BP
• clinical use: stimulate heart

Question 14

Dopamine

Answer 14

• activates alpha and beta adrenergic receptors
• therapeutic dose: stimulates beta 1 of heart
• high dose: activates alpha receptors and cause vasoconstriction
• also activates dopaminergic receptors in renal vasculature (increases blood flow to kidneys)
• clinical uses: shock and CHF

Question 15

Dobutamine

Answer 15

• beta 1 receptor agonist
• increase contractility and HR
• more beta 2 than alpha 1: mild vasodilation
• clinical uses: acute heart failure

Question 16

Albuterol

Answer 16

• Beta 2 agonist

- relieves bronchoconstriction

Question 17

Terbutaline

Answer 17

• beta 2 agonist
• used in asthma for bronchodilation effect
• used in pregnancy to relax uterus and prevent pre-term labor

Question 18

Fenoldopam

Answer 18

• D1 agonist

- used for hypertensive crisis: vasodilator of coronary and peripheral arteries

Question 19

Phenylephrine

Answer 19

• alpha agonist (more 1 than 2)

- used in hypotension and rhinitis

Question 20

Adrenergic agonist effect on blood vessels

Answer 20

• alpha 1: increase vascular smooth muscle contraction, increases arterial resistance, and increase BP
• Beta 2: vasodilation leading to decrease in BP, bronchodilation in lungs

Question 21

Adrenergic agonist effect on heart

Answer 21

• beta 1
• increase HR (+ chronotropy)
• increase force of contraction (+ inotropy)

Question 22

Adrenergic agonist effects of eye

Answer 22

• alpha 1: increase pupillary dilator muscle contraction (mydriasis)
• alpha 2: decrease aqueous humor production

Question 23

Adrenergic agonist effects on respiratory tract

Answer 23

• beta 2 receptors
• located in bronchial airway
• stimulation relaxes bronchial smooth muscle
• opens the airway
• clinical use: asthma (ex. albuterol)

Question 24

Adrenergic agonist effects of GU tract

Answer 24

• beta 2: decrease uterine tone (relaxes)

- alpha 1 and 2: increase bladder sphincter contraction

Question 25

Adrenergic agonist effects on CNS

Answer 25

• alpha 2 receptors
• elevate mood, make more alert, and suppress appetite
• clinical use: narcolepsy, ADD, weight control
• only adrenergic agonist that get into CNS have these effects

Question 26

Adrenergic agonist effects on total body

Answer 26

• stimulation of all adrenergic receptors (alpha 1/2, beta 1/2)
• anaphylaxis: bronchospam, low BP
• example: epi

Question 27

ADR

Answer 27

• cerebral vascular system effects are most important/life threatening toxicity
• excessive doses of catecholamines reduce blood flow to vital organs or cause excessive cardiac stimulation
• lead to HTN, cardiac arrhythmias, cardiac ischemia leading to MI and heart failure
• primarily occur if heart is already sick

Question 28

Amphetamine

Answer 28

• indirect acting adrenergic agonist
• can prevent NE from being taken back up into presynaptic neuron which leaves more NE in synpatic cleft to bind to adrenergic receptors
• can also enter presynaptic terminal and displace stored NE for release into synpatic cleft

Question 29

Tyramine

Answer 29

• found in fermented foods

- also enters presynaptic terminal and displace stored NE for release into synaptic cleft

Question 30

Ephedrine

Answer 30

• release NE from neuron
• directly stimulates alpha and beta receptors
• clinically use pseduoephedrine as nasal decongestant