Adrenergics - Catecholamines

Question 1

Name the Catecholamines (6).

Answer 1

Norepinephrine, Epinephrine, Isoproterenol, Dopamine, Dobutamine, Methyldopa

Question 2

Norepinephrine. What receptors does it work on?

Answer 2

a1, a2, b1

Question 3

Norepinephrine. Agonist or antagonist?

Answer 3

Agonist

Question 4

Norepinephrine. What are its effects?

Answer 4

Peripheral vasoconstriction (a1 receptor), Increase BP (B1 and A1 receptor), no increase in HR b/c vagal reflex to decrease HR in presence of increased TPR and BP

Question 5

Norepinephrine. Therapeutic uses (2).

Answer 5

Vasoconstrictor in intensive care situations

Elevate blood pressure during reduced sympathetic tone -> anesthesia, or neural injury

Question 6

Epinepherine. What receptors does it work on?

Answer 6

A1, A2, B1, B2

Question 7

Epinepherine. Agonist or antagonist?

Answer 7

Agonist

Question 8

Epinephrine. What are its effects? CV, Respiratory, and Metabolic

Answer 8

CV - Increase HR, no net change in BP, slight decrease in PVR
Respiratory - Bronchodilation (B2 receptor)
Metabolic - gluconeogenesis, glycogenolysis, lipolysis, inhibit insulin release (b2 receptors)

Question 9

Epinephrine. Explain the CV effects of this drug.

Answer 9

Increase in HR b/c of increase in contractile force and AV node conduction b/c direct stimulation of B1 Receptor.
No change in BP b/c increase in systolic but decrease in diastolic BP (b2 receptor)
Decrease in TVR b/c dilation of skeletal muscles via B2 receptor even with construction of other vessels via A receptors.

Question 10

How is epinephrine administered?

Answer 10

Parentrally

Question 11

Epinephrine. What receptor is most acted on?

Answer 11

B2

Question 12

Explain the dose dependent CV effects of Epinephrine.

Answer 12

Moderate dose -> vasodilation b/c direct action of b2 receptors on skeletal muscle vessels -> dilation
Higher dose -> vasoconstriction b/c b receptors are full so drug starts binding to a receptors causing vasoconstriction of all vessels

Question 13

Epinephrine. Therapeutic uses (4)

Answer 13

Rapid relief of hypersensitivity
Opthalmic -> pupil dilation
With local anesthetics (vasoconstriction) to increase time of action
Bradyarrhythmias -> restore contractility/rhythm in pts with cardiac arrest

Question 14

Isoproterenol. What receptors does it bind?

Answer 14

B1, B2

Question 15

Isoproterenol. Agonist or antagonist?

Answer 15

Agonist

Question 16

Isoproterenol. What are its effects. CV, Respiratory

Answer 16

CV - Decrease BP and TVR (b/c b2 receptor and vasodilation), increase HR b/c direct stimulation of B1 receptor AND feedback from dec. BP
Respiratory - bronchodilation

Question 17

What are the therapeutic uses of isoproterenol?

Answer 17

In emergencies to stimulation HR during bradycardia or heart block.

Question 18

Is dopamine an antagonist or agonist?

Answer 18

Agonist

Question 19

What receptors does dopamine act one?

Answer 19

DA1, A1, B1

Question 20

What are the CV effects of dopamine - low dose?, medium dose?, high dose?

Answer 20

Low dose - 0.5ug/kg -> acts in DA1 receptor to increase renal blood flow by dilating renal vasculature
Medium dose - 5-10ug/kg -> acts on B1 receptor to increase HR and contractility (increase CO)
High Dose - 10-20ug/kg -> acts on A1 receptor, vasoconstriction and increase TPR

Question 21

What are the therapeutic uses for dopamine?

Answer 21

severe decompensated heart failure, shock

Question 22

Is dobutamine an agonist or antagonist?

Answer 22

Mixed b/c racemic

Question 23

What receptors does dobutamine act on? (-, +, Racemic)

Answer 23

(-) -> a1 agonist, b agonist
(+) -> a1 antagonist, b agonist
Racemic -> b1 agonist

Question 24

What are the therapeutic effects of dobutamine?

Answer 24

Increase HR and contractility, minimal change in BP and TPR

Question 25

What are the therapeutic uses of dobutamine? (2)

Answer 25

Short term treatment of cardiac decompensation | Cardiac stress testing -> stress the heart to do the testing of pt is unable to exercise

Question 26

What is significantly unique about methyldopa?

Answer 26

Orally active prodrug

Question 27

What receptor does methyldopa act on?

Answer 27

A2

Question 28

Is methyldopa an agonist or antagonist?

Answer 28

agonist

Question 29

What are the effects of methyldopa?

Answer 29

decrease peripheral R, decrease HR, decrease CO

Question 30

What is the major therapeutic use of methyldopa?

Answer 30

HTN, especially gestational b/c been proven to be safe for baby

Question 31

What are the side effects of methyldopa? (4)

Answer 31

Sedation, dry mouth, edema, rebound HTN with sudden discontinuation

Question 32

Explain the mechanism of action of methyldopa?

Answer 32

a-methyldopa -> CNS nerve cell ->decarboxylated by acid decarbozylase now is a-methyldopamine -> to storage granules via transporter -> converted to a-methylnorepinepherine by dopamine hydrozylase -> released instead of NE and acts on a2 receptors IN CNS

Question 33

What prevents methyldopa deradation by MAO? What is the significance of that clinically?

Answer 33

alpha methyl group prevents degradation -> reason it can be given orally, long half life