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Pharmacology > Drugs of the Sympathetic Nervous System > Flashcards

Drugs of the Sympathetic Nervous System Flashcards

1
Q

Define sympathomimetic drug

A

A drug which mimics the effect of adrenergic sympathetic stimulation

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2
Q

Name 3 of the most important clinical uses for sympathomimetic drugs

A
  1. Bronchial asthma
  2. To increase blood pressure
  3. Constriction of blood vessels in mucosa
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3
Q

Name the 2 types of sympathomimetics, based on chemical structure

A
  1. Catecholamines

2. Non-catecholamines

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4
Q

Give 4 examples of Catecholamines

A
  1. NA
  2. Adrenaline
  3. Isoprenaline
  4. Dopamine
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5
Q

Give 4 examples of non-catecholamines

A
  1. Phenylephrine
  2. Ephedrine
  3. Phenyl-propanolamine
  4. Nafasoline
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6
Q

Which catecholamine is synthetic?

A

Isoprenaline

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7
Q

Which non-catecohlamines are synthetic?

A

All

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8
Q

Describe the chemical structure of catecholamines

A

Substitutions at the alpha, beta positions of the benzene ring and N-atom

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9
Q

Describe the chemical structure of non-catecholamines

A

No catechol nucleus

Substitutions at the alpha & beta C-atoms, Benzene ring or Terminal amino group

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10
Q

How are catecholamine administered?

A

Parenterally, sublingually or per aerosol

Too rapidly metabolised by liver if taken orally - 1st pass effect

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11
Q

How are non-catecholamines administered?

A

Orally

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12
Q

Compare the duration of action for catecholamines and non-catechlamines

A

Catecholamines - Brief (does not penetrate BBB)

Non-catecholamines - Long

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13
Q

Compare the direct vs indirect mechanism of action of sympathomimetics

A 
Direct:  
  - Directly activates receptor
  - At least 2 correct substitutions on para & meta positions of benzene ring as well as on beta C-atom (usually OH)
  - 
Indirect:  
  - Release NA from vesicle stores  
  - 1 or no substitution (not on benzene ring)
       <2 OH on ring decrease COMT
       CH3 on alpha C-atom decrease MOA
  - Longer acting
  - Can cause tachyphylaxis
  - Can be mixed: partially activates receptor & replacing NA
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14
Q

Define tachyphylaxis

A

A decreased response caused by exhaustion of NA stores

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15
Q

Describe the structure-activity relationship of sympathomimetics

A

Catecholamine do not stimulate all adrenergic receptors to the same degree.
- Depends on substitution on N-atom
eg. NA stimulates alpha receptors
Adrenaline stimulates alpha & beta receptors
Isoprenaline stimulates B receptors
- Also dose dependant
eg. NA can stimulate beta 1 receptors in high doses
Adrenaline 1st produce beta-effect, then alpha effect if
certain threshold is reached

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16
Q

Explain why catecholamines are mainly used as emergency drugs

A

The potency and action of various receptors limits clinical use of these drugs

17
Q

What are the clinical uses of Isoprenaline?

A

Dilates bronchi (beta 2)
Also stimulates heart, causing dysrhythmias & ventricle fibrillation (beta 1)
Can be used in cardiac arrest (administered close to the heart)

18
Q

What are the clinical uses of Adrenaline and NA?

A

Vasoconstrictors (alpha 1) - combined with local anaesthetics.
Adrenaline can be used in allergic reactions (anaphylactic shock) due to anti-histamine effect.
Adrenaline can be used in cardiac arrest (administered close to the heart)

19
Q

Name a clinical use if Dopamine

A

Increases blood pressure in shock

20
Q

Name 2 catecholamines which can be used in cardiac arrest

A

Adrenaline

Isoprenaline

21
Q

Give a broad overview the various SNS drugs

A
  1. Sympathomimetics
  2. 1 Chemical classification:
  3. 1.1 Catecholamines
  4. 1.2.Non-catecholamines
  5. 2 MOA classification:
  6. 2.1 Direct
  7. 2.1.1 B1 adrenergic agonist
  8. 2.1.2 B2 adrenergic agonist
  9. 2.2 Indirect/Mixed
  10. Adrenergic receptor agonists
  11. 1 alpha antagonist
  12. 2 beta antagonists
  13. 3 alpha & beta antagonists
22
Q

Give an example of a B1-adrenergic agonist

A

Dobutamine

23
Q

List 5 examples of B2-adrenergic agonists

A
  1. Salbutamol
  2. Orciprenaline
  3. Terbutaline
  4. Salmeterol
  5. Formoterol
24
Q

List 6 examples of Indirect/Mixed action drugs

A
  1. Phenyleprhine
  2. Ephedrine
  3. Phenylpropanolamine
  4. Amphetamine
  5. Naphazoline
  6. Oxymetazoline
25
Q

List 5 clinical uses for Adrenergic Receptor Antagonists

A
  1. Blood pressure control
  2. Heart function
  3. Migraine
  4. Thyroid dysfunction
  5. Tremors
26
Q

List the 3 types of Adrenergic Receptor Antagonists

A
  1. a-antagonists
  2. B-antagonists
  3. a and B-antagonists
27
Q

List 3 clinically important categories of a-antagonists

A
  1. Haloalkylamines
  2. Imidazolines
  3. Quinazolines
28
Q

List 4 side-effects of a-antagonists

A
  1. Orthostatic hypotension
  2. Tachycardia
  3. Vertigo
  4. Sexual dysfunction
29
Q

List 7 clinical uses for B-antagonists

A
  1. Dysrhythmias
  2. Angina pectoris
  3. Hypertension
  4. Hyperthyroidism (decrease peripheral symptoms)
  5. Glaucoma (decrease prod of watery fluid)
  6. Anxiety (decrease sympathetically-induced symptoms)
  7. Migraines (block craniovascular B-receptors & cause less vasodilation)
30
Q

List 7 side effects of B-antagonists

A
  1. May worsen acute cardiac failure
  2. Bronchospams (esp non-selective)
  3. Hypoglyceamia
    • antagonise catecholamine-induced mobilisation of
      glycogen
    • Mask S&S of hypoglycaemia in IDDM
  4. Bradycardia / heart block
  5. Fatigue (decreased exercise tolerance)
  6. Cold extremities
  7. Nightmares / vivid dreams
31
Q

Describe how the structure of a drug determines whether it’s an agonist or and antagonist

A

B interaction rather than alpha if substitute on N-atom is enlarged.
Free H-atom on N-atom -> little/no activity
OH-group on B C-atom -> l form for biological activity
B-blockers:
- OH groups on aromatic ring omitted
- Aromatic substituent of enthanolamine side chain is separated by oxymethalene bridge

Pharmacology (3 decks)

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