Pharm for the neuromuscular junction Flashcards

1
Q

What is a cholinesterase inhibitor? How does it work?

A
  • Binds to AChesterase at NMJ (and other Ach receptor sites)
  • Peripherally leads to increase electrical firing at the NMJ – often manifested as skeletal muscle twitching
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2
Q

What is a neuromuscualr junction nicotinic receptor antagonist?

A
  • Sits in AChR and blocks transmission of electrical activity
  • Reduces activity of neuromuscular junction
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3
Q

What is a glucocorticoid-sparing immunosuppressive drug?

A
  • Alternate immunosuppressive drug than GCS. These alternative drugs usually take longer to have an immunosuppressive effect
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4
Q

What are the two cholinesterase inhibitors?

A

They can exist as:
- therapeutics (pyridostigmine neostigmine)
- Toxin (organophosphates)

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5
Q

What happens if an animal is exposed to organophosphates?

A
  • Salivation
  • lacrimation
  • urination
  • Diarrhoea
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6
Q

Is there an antidote for patients exposed to organophosphates?

A

Yes, an antidote for organophosphate toxicity is called pralidoxime or 2-PAM. It binds to the organophosphate releasing the AChE

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7
Q

Explain what is happening in this diagram (myasthenia gravis)

A
  • Immune mediated attack on the nicotinic receptors
  • In MG, antibodies are produced that binds to, & blocks NMJ AChR (acetylcholine receptor). Therefore fewer binding sites for ACh, has an effect on the signal getting through to the muscles
  • Leads to accelerated AChR endocytosis & degradation
  • Activate complement that damages muscle fibres
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8
Q

How would you diagnose Myasthenia gravis (MG)?

A
  • Use a cholinesterase inhibitor - binds to NMJ AChE allowing Ach longer action at the fewer nicotinic receptors that are available due to antibody attack
  • Edrophonium - tensilon - short acting diagnostic drug
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9
Q

How would you treat MG?

A

You would use a longer acting cholinesterase inhibitor, these include:
- Pyridostigmine (mestinon)
- Neostigmine (prostigmin)

Other immunosuppressive drugs are also used in treatment

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10
Q

Give some examples of important immunosuppressive drug classes.

A
  • Glucocorticosteroids (prednisolone, methylprednisolone, dexamethasone)
  • Antimetabolites (azathioprine, mycophenolate, mofetil)
  • alkylating agents (chlorambucil)
  • Immuneophilin ligands (cyclosporine, tacrolimus)
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11
Q

Can the immunosuppressive drug asathioprine be used in cats?

A

No, an alkylating agent (chlorambucil) is used instead

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12
Q

What drug would you use to reverse antagonists of NMJ nicotinic receptors?

A

Cholinersterase inhibitor

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13
Q

What are the actions of Antagonists of NMJ nicotinic receptors?

A
  • Muscular paresis/paralysis
  • Not a therapeutic treatment
  • Only used during general anaesthesia to assist with mechanical ventilation
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14
Q

What drug reverses the action of antagonists of NMJ nicotinic receptors?

A

Cholinesterase inhibitors

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15
Q

Why might botulinum toxin be used in veterinary medicine?

A
  • Sometimes used to treat entropian, is releives skeletal muscle spasticity. Inhibits ACh release from presynaptic membrane at NMJ
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