Myasthenia Gravis

Question 1

MG

Answer 1

autoimmune dx char by fluctuating weakness in oculobulbar, limb, and respiratory tracts

Question 2

What antibodies are involved in MG?

Answer 2

anti-ACHR antibodies

Question 3

MG disease course

Answer 3

mild with remission periods then back to baseline
- short term remission, stabilization, severe progression
- varies tho

Question 4

Risk fx for MG

Answer 4

women, 10-65y
- genetic and environmental interaction

Question 5

What are AChR

Answer 5

Acetylcholine receptors in the NMJ of the skeletal muscle

Question 6

MG patho

Answer 6

• anti-AChR antibodies attack the nicotinic ACh post-synaptic receptors (receivers)
• receptors/binding is blocked
• not enough sites for ACh to bind now

Question 7

What does ACh do?

Answer 7

dec HR, inc body secretions, smooth muscle ctx, dilated BVs

Question 8

CM of MG

Answer 8

• fluctuating skeletal weakness
• strength may return after rest
• facial muscles involved first–face, eyes, speak, breathe (asp, drool, malnut)
  -muscle fatigue after exercise
• s/s often appear in preg, PP, or after anesthesia

Question 9

Myasthenic crisis

Answer 9

Acute exac of muscle weakness from lacking ACh
- triggered by infx, surg, emo distress, preg/menses, poor pharm control
- improves with edophronium

Question 10

Big comp of Myasethnic crisis

Answer 10

Breathing weakness and resp arrest

Question 11

Pharm for MG

Answer 11

• immunosuppressants (steroids)
• cholinesterase inhibitors

Question 12

Cholinesterase inhibitors

Answer 12

• prevent the breakdown of ACh by cholinesterase to keep higher levels of ACh
• intensity fx of ACh release from motor neurons
• give 30-45min before eating
• for symptomatic
• affects nic and musc rec even tho MG only affects nic

Question 13

Cholinergic crisis

Answer 13

• excess weak and paralysis
• excess muscarinic ACh stim
• can cause overstim of pt smooth muscles and resp fail, diarrhea, diaphoresis, brady, inc sec, pupil constriction
• tx with venilator and ATROPINE
• pt needs med alert bracelet
• won’t improve if given edrophonium

Question 14

Neostigmine (Prostigmin) class and MOA

Answer 14

• Cholinesterase inhibitor (Anticholinesterase); Cholinergic
• Parasympathomimetic, enhances cholinergic action by facilitating transmission of impulses across neuromuscular junctions; affect muscarinic (glands) and nicotinic receptors (skeletal and adrenal)

Question 15

Neostigmine (Prostigmin) SE

Answer 15

MUSCARINIC - Inc motility, diarrhea, inc secretions, urinary urgency, bradycardia, bronchial constriction, miosis (constriction and near-sightedness)
NICOTINIC - inc muscle ctx and cholinergic crisis

Question 16

Neostigmine (Prostigmin) NC

Answer 16

• Can give atropine with to decrease mouth secretions
• therapeutic doses inc muscle ctx
• toxic doses dec ctx and can lead to cholinergic crisis (atropine is antidote)
• affects muscarinic and nicotinic receptors
• watch with asthma

Question 17

Edrophonium

Answer 17

• short acting cholinesterase inhibitor
• inc ACh temporarily
• for MG crisis