SNS agonists

Question 1

Recall the type of adrenoceptor present in the heart, blood vessels and lungs respectively

Answer 1

beta 1, alpha 1, beta 2

Question 2

What aspects of anaphylaxis are combatted by AD treatment?

Answer 2

Bronchoconstriction, bradycardia, vasodilation

Question 3

Recall 5 clinical uses of adrenaline

Answer 3

Anaphylaxis
Asthma
Acute bronchospasm
Anaesthesia
Cardiogenic shock

Question 4

How does AD combat cardiogenic shock?

Answer 4

Targets beta 1 receptor to help heart pump blood

Question 5

Why is AD used in anaesthesia?

Answer 5

Maintains BP and prolongs bronchoconstriction in spinal anaesthesia via alpha 1 targetting

Question 6

Recall 5 possible side effects of AD use

Answer 6

1. Tachycardia can exacerbate arrythmias
2. Thickened secretions
3. SKeletal muscle tremor
4. Cold extremities
5. Hypertension

Question 7

Recall 5 selective adrenoceptor agonists and their selectivities

Answer 7

Isoprenaline - beta
Clonidine - alpha 2
Phenylephrine - alpha 1
Dobutamine - beta 2
Salbutamol  - beta 2

Question 8

Recall the pathophysiology of cardiogenic shock

Answer 8

LV dysfuntion –> decreased CO –> lack of tissue perfusion –> shock

Question 9

Describe the duration of action of phenylephrine

Answer 9

Long-lasting because resistant to COMT breakdown

Question 10

What drug (and it’s class) should be used as a nasal de-contestant and why?

Answer 10

Phenylephrine (alpha agonist) - reduces blood vessel dilation in nose

Question 11

What is a midriatic?

Answer 11

Something that dilated the pupil

Question 12

Which class of drugs make good midriatics?

Answer 12

Alpha agonists

Question 13

What is clonidine’s main clinical use?

Answer 13

Glaucoma treatment

Question 14

How does clonidine treat glaucoma?

Answer 14

Stimulates alpha 1 on blood vessels to reduce blood supply to ciliary body

Question 15

What 2 receptors are present on the ciliary body and what are their roles?

Answer 15

Beta 1: humour production

Alpha 2: decreases beta 1 response

Question 16

Recall 3 uses of clonidine

Answer 16

Glaucoma, hypertension, migraine

Question 17

How does clonidine treat hypertension?

Answer 17

Agonises alpha 2 receptors to reduce SNS tone in vasculature

Question 18

How does clonidine act to treat migraine?

Answer 18

Agonises alpha 2 to reduce beta-2 stimulated dilation of blood vessels

Question 19

Describe the duration of action of isoprenaline

Answer 19

Long-lasting because resistant to MAO uptake

Question 20

Recall 3 uses of isoprenaline

Answer 20

Cardiogenic shock, acute heart failure, MI

Question 21

Why does isoprenaline have a risk of exacerbating arrythmia?

Answer 21

If you stimulate beta 2 –> venous BP falls –> increased baroreceptor firing

Question 22

Which drug has been superceded by dobutamine?

Answer 22

Isoprenaline

Question 23

Why is dobutamine a better drug than isoprenaline generally?

Answer 23

Less likely to cause reflex tachycardia as is more selective for beta 1 than beta 2

Question 24

Describe the duration of action of dobutamine

Answer 24

Very short half life as highly susceptible to COMT breakdown

Question 25

What is the mechanism of action of salbutamol in asthma treatment?

Answer 25

Reduces ability of SMCs to contract:

1. Decreases PI hydrolysis –> less calcium released from stores
2. Increases Na+/Ca2+ exchange
3. Opens K+ channels so cell much more likely to be hyperpolarised

Question 26

What does PI hydrolysis do normally?

Answer 26

Stimulates Ca++ release from intracellular stores to initiate SMC contraction

Question 27

Why is salbutamol used in labour?

Answer 27

Reduces ability of uterine muscle to contract

Question 28

Recall 2 uses of phenylephrine

Answer 28

1. Nasal decongestant

2. Mydriatic

Question 29

Why is isoprenaline useful in cardiogenic shick?

Answer 29

Activates beta 2 –> Reduces BP –> increased heart stimulation