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Pharma > Indirect Sympathomimetics. Selective a1 agonists. Select alpha 2 agonists and drugs acting on the imidazoline receptors. > Flashcards

Indirect Sympathomimetics. Selective a1 agonists. Select alpha 2 agonists and drugs acting on the imidazoline receptors. Flashcards

1
Q

Indirect sympathomimetics: Name the Releasers

A
  • Amphetamine
  • Tyramine
  • Ephedrine
  • Norpseudoephedrine
  • Modanifil
  • Methylfenidate
  • Dexmethylfenidate
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2
Q

Amphetamine

  • Action
  • Clinical use
  • Characteristics
A
  • Amphetamine is an indirect sympathomimetic
  • It promotes the release of NT from the nerve terminals

Action:

  • Amphetamine increases the BP - (via a1 (vasculature) and b1 (heart) stimulation)
  • Psychostimulant: it is a mood stimulant and increases alertness
  • When it is abused it can result in euphoria
  • Decreases appetite

Clinical use:
- ADHD

Characteristic:

  • Orally active
  • Long action of duration
  • Enters CNS very easily and releases biological amines
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3
Q

Tyramine:

  • Clinical use
  • Characteristics
  • Treatment
A
  • Tyramine is a releaser

Clinical use:
- It is not clinically used

Characteristics:

  • Tyramine is present in foods such as cheese and red wine.
  • It is metabolised and inactivated by MAO-A in the GIT
  • On those in MAO-A inhibitors that injest tyramine means that tyramine is not inactivated by MAO-A and therefore tyramine reaches the systemic circulation and increases the sympathetic tone by releasing NE
  • Results in hypertensive crisis

Treatment:
- Treatment of tyramine induced hypertensive crisis is Phentolamine (a non selective alpha receptor antagonist)

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4
Q

Norpseudoephedrine:

  • Clinical use
  • Characteristic
A
  • Norpseudoephedrine is a releaser

Clinical use:
- Nasal decongestant

Characteristics:
- Used with ibroprofen and antihistamines

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5
Q

Modanifil

- Clinical use

A
  • Modanifil is a releaser

Clinical use:
- Narcolepsy

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6
Q

Methylfenidate

- Clinical use

A
  • Methylfenidate is a releaser

Clinical use:
- ADHD

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7
Q

Dexmethylfenidate

- Clinical use

A
  • Dexmethylfenidate is a releaser

Clinical use:
- ADHD

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8
Q

Cocaine:

  • Action
  • Clinical use
  • Adverse effects
  • Treatment
A
  • Cocaine is a reuptake inhibitor

Action:

  • It blocks dopamine and NE reuptake by blocking the Na+/K+ ATPase in the CNS and the periphery
  • Its sympathomimetic actions in the CNS result in euphoria

Clinical use:
- Local anaesthetic

Adverse effects:

  • Nasal septum perforation - this is because it also has intrinsic alpha 1 receptor agonist action and therefore causes vasoconstriction leading to nasal ischemia.
  • Dilated cardiomyopathy
  • Drug abuse

Treatment:
- Phentolamine

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9
Q

TCA: Desipramine and Amitriptyline

  • Action
  • Clinical use
  • Adverse effects
A
  • TCAs are reuptake inhibitors

Action:
- They block NE reuptake in the CNS and the periphery

Clinical use:
- Depression

Adverse effects:

  • Arrhythmias
  • Change in BP
  • alpha and M blockers may complicate their autonomic actions
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10
Q

Name the TCA

A
  • Amitryptyline

- Desipramine

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11
Q

Name the irreversible non-selective MAO inhibitors

A
  • Tranylcypromine
  • Phenelzine
  • Pargyline
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12
Q

What is are Tranylcypromine, Phenelzine and Pargyline used for?

Why are they no longer recommended?

A
  • Depression

- No longer used as they are non-selective MAO inhibitors so the ingestion of Tyramine can result in Hypertensive crisis

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13
Q

Name the irreversible MAO-B inhibitors

A

Selegiline

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14
Q

What is Selegiline used for?

A

Parkinsons

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15
Q

What type of MAO inhibitor is Selegiline?

A

Irreversible MAO-B inhibitor

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16
Q

What does MAO-A metabolise?

A

NE and serotonin

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17
Q

What does MAO-B metabolise?

A

Dopamine and tyramine

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18
Q

Name the reversible MAO-A inhibitors

A

Moclobemid

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19
Q

What is Moclobemid used for?

A

Mental depression

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20
Q

What type of MAO inhibitor is Moclobed?

A

Reversible MAO-A inhibitor

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21
Q

What are the selective alpha 1 agonists?

A

Phenylephrine
Methoxamine
Midodrine

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22
Q

Phenylephrine

  • Action
  • Clinical use
  • Characteristics
A

Action:

  • Phenylephrine is a selective alpha 1 receptor agonist
  • It results in vasoconstriction which increases BP

Clinical use:

  • Nasal decongestant (topical or oral)
  • Ophthalmologic use (mydriasis without cycloplegia)
  • Hypovolemia or shock: increased SBP and DBP results in reflex bradycardia

Characteristics:

  • Not used as a systemic drug as it is dangerous
  • It replaces pseudoephedrine as a nasal decongestant
  • It is not inactivated by COMT as it is a catechol derivative
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23
Q

What sort of drug is Phenylephrine?

A

It is a selective alpha 1 receptor agonist

24
Q

What are the clinical uses of Phenylephrine?

A
  • Nasal decongestant (topical or oral)
  • Hypovolemia or shock
  • Ophthalmologic uses
25
Q

What is the mechanism of action of Phenylephrine?

A

It results in vasoconstriction which increases BP

26
Q

What is the mechanism of action of Methoxamine?

A

It results in vasoconstriction which increases BP

27
Q

What is the mechanism of action of Midodrine?

A

It results in vasoconstriction which increases BP

28
Q

When do we use Methoxamine?

A
  • Paroxysmal atrial tachycardia (PAT) through the vagal reflex
29
Q

How is Methoxamine administered?

A
  • Parenteral use
30
Q

Methoxamine:

  • Action
  • Clinical use
  • Characteristic
A

Action:

  • Methoxamine is a selective alpha 1 receptor agonist
  • It results in vasoconstriction which increases the BP

Clinical use:
- PAT through the vagal reflex

Characteristic:
- Parenteral use

31
Q

Midodrine:

  • Action
  • Clinical use
  • Characteristcs
A
  • Midodrine is a selective alpha 1 receptor agonist
  • it results in vasoconstriction that increases the BP

Clinical use:
- Orthostatic hypotension due to impaired ANS

Characteristics:
- Prodrug that is enzymatically hydrolysed to desglymidodrine, which is a selective a1 agonist

Adverse effects:
- Hypertension when patient is supine

32
Q

What is Midodrine used for?

A

Orthostatic hypotension due to impaired ANS

33
Q

Which alpha 1 receptor agonist is a prodrug?

What is the prodrug converted to?

A

Midodrine

Desglymidodrine

34
Q

What are the adverse effects of Midodrine?

A

Hypertension when the patient is supine

35
Q

What are the selective alpha 2 agonists?

A 
Clonidine
Methyldopa
Guaficine
Tizanidine
Dexmedetomidine
36
Q

Clonidine:

  • Action
  • Clinical use
  • Characteristics
  • Adverse effects
A
  • Clonidine is a selective alpha 2 agonist

Action:

  • Centrally: it acts on the presynaptic alpha 2 receptors in the solitary tract nucleus of the medulla, resulting in a decrease in BP
  • Peripherally:
  • acts on alpha 2 receptors resulting in negative feedback
  • It stimulates I1 receptors in rostral ventrolateral medulla which results in a decrease of SY outflow

Clinical use:

  • Hypertension
  • Nasal decongestant
  • Perianesthetic medication
  • Diarrhoea in diabetics
  • ADHD
  • Glaucoma
  • Minimizes symptoms of withdrawal from opiates, tobacco and benzodiazepine

Characteristics:

  • Imidazole derivative
  • Do not use in sedation, xerostomia and constipation as they are parasympatholytic effects

Adverse effects:

  • Lethargy
  • Sedation
  • Constipation
  • Xerostomia
  • Rebound HTN if there is abrupt discontinuation of the drug
37
Q

What are the clinical uses of Clonidine?

A
  • Hypertension
  • Nasal decongestant
  • Perianesthetic medication
  • Diarrhoea in diabetics
  • ADHD
  • Glaucoma
  • Minimizes symptoms of withdrawal from opiates, tobacco and benzodiazepine
38
Q

What are the adverse effects of Clonidine?

A
  • Lethargy
  • Sedation
  • Constipation
  • Xerostomia
  • Rebound HTN if there is abrupt discontinuation of the drug
39
Q

What is the action of Clonidine?

A
  • Centrally: it acts on the presynaptic alpha 2 receptors in the solitary tract nucleus of the medulla, resulting in a decrease in BP
  • Peripherally:
  • acts on alpha 2 receptors resulting in negative feedback
  • It stimulates I1 receptors in rostral ventrolateral medulla which results in a decrease of SY outflow
40
Q

What type of drug is Guaficine?

A

It is a selective alpha 2 agonist

41
Q

What is the action of Guaficine?

A

Centrally acting selective alpha 2 agonist

42
Q

What is Guaficine used for?

A

HTN

43
Q

What type of drug is methyldopa?

A

It is a selective alpha 2 agonist

44
Q

Methyldopa:

  • Action
  • Clinical use
  • Characteristics
A

Action

  • Methyldopa enhances the negative feedback at NE terminals
  • It is a competitive inhibitor of DOPA-decarboxylase

Clinical use:

  • Mild to moderate HTN
  • HTN in pregnancy
45
Q

What does Methyldopa inhibit?

A

It is a competitive inhibitor of DOPA-decarboxylase

46
Q

What are the clinical uses of Methyldopa?

A
  • Mild to moderate HTN

- HTN in pregnancy

47
Q

What type of drug is Tizanidine?

A

It is a selective alpha 2 receptor agonist

48
Q

What is Tizanidine used for?

A

Centrally acting skeletal muscle relaxant

49
Q

What are the adverse effects of Tizanidine?

A

Sedation

50
Q

What type of drug is Dexmedetomidine?

A

It is a selective alpha 2 receptor agonist

51
Q

What is Dexmedetomidine used for?

A

Sedation of initially intubated and mechanically ventilated patients during treatment in the ICU

52
Q

Which drugs act on the Imidazoline receptors?

A

Moxonidine

Rilmenidine

53
Q

What is Moxonidine and Rilmenidine used for?

A

HTN

54
Q

What is the action of Moxonadine and Rilmenidine?

A
  • They decrease SY out flow

- They have more selective binding to I1 receptors and less affinity to alpha 2 receptors

55
Q

What are the adverse effects of Moxonadine and Rilmenidine?

A
  • Dry mouth (but less than with Clonidine)

- Sedation

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