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Pharmacology RDT Autumn term > Sympathetic nervous system agonists > Flashcards

Sympathetic nervous system agonists Flashcards

1
Q

What are adrenergic receptors?

A

Receptors found in the SNS that use NA/A neurotransmitters.

They are principally used for their actions in CVS, eyes and lungs.

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2
Q

What are the different subtypes of adrenoreceptors?

A

Alpha 1

Alpha 2

Beta 1

Beta 2

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3
Q

What adrenoreceptors are found on the heart?

A

Beta 1

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4
Q

What adrenoreceptors are found on the lungs?

A

Beta 2

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5
Q

Which adrenoreceptors are found on the blood vessels?

A

Mostly alpha 1 but with some beta 2

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6
Q

Which beta receptors are found on the…

  1. eye
  2. trachea and bronchioles
  3. liver
  4. adipose tissue
  5. kidney
  6. ureter and bladder
  7. Blood vessels (skin)
  8. Blood vessels (skeletal muscle)
  9. GI
  10. Heart
  11. Skin
  12. Salivary glands

…?

A
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7
Q

How is Noradrenaline metabolised?

A

NA is made in nerve terminals whereas adrenaline is synthesised in the adrenal medulla.

  1. Tyrosine –> DOPA (via tyrosine hydroxylase)
  2. DOPA –> dopamine ( via DOPA decarboxylase)
  3. Dopamine –> NA (via dopamine ß-hydroxylase, inside the vesicle)
  4. Vesicle fuses with membrane and exocytosis of NA occurs
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8
Q

What is the role of the alpha 2 adrenoreceptor with NA release?

A

There is an alpha 2 receptor present on the pre-junctional receptor.

It is like a feedback receptor. It controls the release of NA by negative feedback and suppresses NA exocytosis

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9
Q

What will alpha 2 adrenoreceptor agonists do?

A

They will bind to the pre-synaptic alpha 3 adrenoreceptor and will suppress sympathetic function by suppressing NA release.

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10
Q

Name a non-selective SNS agonist?

*another term for SNS agonist is adrenoreceptor agonist

A

Adrenaline

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11
Q

Name an alpha-1 selective SNS agonist

A

Phenylephrine

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12
Q

Name an alpha-2 selective SNS agonist

A

Clonidine

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13
Q

name beta-1 selective SNS agonists

A

Dobutamine

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14
Q

Name a Beta-2 selective SNS agonist

A

Salbutamol

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15
Q

What is used for the treatment of anaphylaxis?

A

A shot of adrenaline is administered via EpiPen to someone in anaphylaxis. Remember that adrenalin is a non-selective SNS agonist.

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16
Q

What happens in an anaphylactic reaction?

A
  • Airways- there is reduced breathing as anaphylaxis causes bronchoconstriction and difficulty swallowing
  • Heart- anaphylaxis causes hypotension
  • Vascular tone- anaphylaxis causes peripheral vasodilation
  • GI- contraction of smooth muscle (cramps), vomiting diarrhoea
17
Q

What causes anaphylaxis?

A

Antigen in bloodstream enters tissues and activates connective tissue mast cells throughout the body.

Mast cells degranulate and release inflammatory mediators.

18
Q

How does adrenaline treat anaphylaxis?

A
  • Airways- adrenaline will bind to beta-2 receptors causing bronchodilation
  • Heart- adrenaline will bind to beta-1 receptors causing tachycardia (positive inotropic and chronotropic effect). This will help to restore BP
  • Vascular tone- adrenaline will bind to alpha 1 receptors causing vasoconstriction. This will increase TPR and help to raise BP.
  • Adrenaline will also supress mediatior release.
19
Q

Is adrenaline more beta or alpha sensitive?

A

Adrenaline is more beta sensitive

NA is more alpha sensitive

20
Q

Name 5 other clinical uses of adrenaline

A
  • Bronchospasm (for airways, beta 2 receptors)
  • Cardiogenic shock (beta 1 receptors to have an effect)
  • Spinal anaesthetics (alpha 1 for anywhere else)- maintains BP
  • Local anaesthesia- vasoconstricts (stops it entering the systemic circulation, prolonging the effect).
  • Can also be used for glaucoma- used to managed increased intraocular pressure. Vasoconstricts ocular blood vessels, reducing blood flow and thus the production of aqueous humour- targets the alpha 1 receptors.
21
Q

What are the unwanted effects of adrenaline?

A
  • Secretions – reduced and thickened mucous (more of an immune effect)
  • CNS – minimal
  • CVS effects
  • tachycardia, palpitations, arrhythmias
  • cold extremities, hypertension
  • overdose – cerebral haemorrhage, pulmonary oedema
  • GIT – minimal
  • Skeletal muscle - tremor
22
Q

what is the use of the alpha 1 selective drug phenylephrine?

A

It is very similar (structurally) to adrenaline- except one hydroxyl group. This change makes it alpha 1 selective. It is most resistant to breakdown by COMT and MAO.

It is good for acting on peripheral tissues and is found in cold medicine. It vasoconstricts blood vessels

23
Q

What are the main effects of phenylephrine?

A
  • Mydriatic (dilate pupils)
  • Nasal decongestant (less white cell infiltration and build-up of mucus/ fluids)
  • Will bring BP up (vasoconstriction)
24
Q

What does the alpha-2 selective drug do?

A

Clonidine is the agonist of the pre-junctional alpha 2 receptor- the negative feedback one. The result is sympathetic antagonism as NA is not being released.

25
Q

What are the clinical uses of clonidine?

A
  • Treatment of hypertension/ migraines
  • Reduces sympathetic tone- NA is being inhibited. Central brainstem action within the baroreceptor pathway to reduce sympathetic outflow. Clonidine can inhibit sympathetic nerves from firing.
26
Q

What is glaucoma?

A

Characterised by an increase in intraocular pressure. Caused by poor drainage of aqueous humour (produced by the ciliary body).

People with glaucoma, venous channels blocked so humour can’t be drained and if the pressure is too great, there are dysfunctional vessels, damages optic nerve and can cause blindness.

27
Q

Which adrenoreceptors are located in the eyes?

A

Alpha 1 and 2

28
Q

What is used in the treatment of glaucoma?

A

Treatment is targetting the alpha 1 and alpha 2 receptors (agonists).

Binding to the alpha 1 causes vasoconstriction

Binding to the alpha 2 receptor causes a reduction in humour formation.

29
Q

What is isoprenaline?

A

SNS agonist that is selective to both beta equally over both alpha receptors. It is chemically related to adrenaline and more resistance to MAO and uptake 1.

It has a fast plasma half-life of 2 hours

30
Q

What are the clinical uses of isoprenaline?

A

used for:

Cardiogenic shock

Acute heart failure

Myocardial infarction

31
Q

What is the rebound tachycardia reflex?

A

The beta 2 stimulation of smooth muscle in skeletal muscle will cause venous BP to drop which is not ideal in this situation. This triggers a rebound reflex tachycardia and stimulation of baroreceptors

32
Q

What is dobutamine? and what is it used for?

A

It is a beta 1 selective SNS agonist.

It is used in emergencies- for cardiogenic shock as it lacks the tachycardia reflex that isoprenaline has.

it has an extremely short half-life on 2 minutes and is rapidly metabolised by COMT.

33
Q

What is salbutamol and what are its actions?

A

Similar to adrenaline but resistant to breakdown from COMT and MAO. Inhaling into the airways and binds to beta 2 receptors. Beta 2 is coupled with cAMP and leads to hyperpolarisation of the cell. Leads to muscle relaxation and bronchodilation

34
Q

What are the clinical uses of salbutamol?

A

Treatment of asthma

    • b2-relaxation of bronchial smooth muscle
    • inhibition of release of bronchoconstriction from mast cells.

Treatment of threatened premature labour

    • b2-relaxation of uterine smooth muscle
35
Q

What are the side effects of salbutamol?

A

Reflex tachycardia, tremor, blood sugar dysregulation

Pharmacology RDT Autumn term (10 decks)

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