Myasthenia Gravis

Question 1

what is myasthenia gravis?

Answer 1

–autoimmune
–characterized by fluctuating weakness of certain muscle groups

Question 2

course of disease for MG

Answer 2

variable
–short term remission
–stabilization
–severe, progression

Question 3

risk factors for MG

Answer 3

–age: 10-65 years
–women

Question 4

patho for MG

Answer 4

–antibodies attack ACh receptors
–decrease in ACh receptor sites at the neuromuscular junction
–prevents ACh molecules from attaching and stimulating muscle contraction

Question 5

symptoms of MG

Answer 5

–fluctuating weakness of skeletal muscle
–strength comes back after resting

Question 6

what muscles are involved in MG?

Answer 6

–eyes/eyelids
–facial
–speaking
–breathing

Question 7

myasthenic crisis

Answer 7

acute exacerbation of muscle weakness

Question 8

what is a myasthenic crisis triggered by?

Answer 8

–infection
–surgery
–emotional distress
–pregnancy/menses
–inadequate pharmacotherapy or other drugs

Question 9

major complication of myasthenic crisis

Answer 9

breathing muscle weakness

Question 10

MG pharm

Answer 10

–immunosuppressants (steroids)
–cholinesterase inhibitors

Question 11

how do cholinesterase inhibitors work?

Answer 11

–prevent inactivation of ACh by cholinesterase
–intensify effects of ACh released from motor neurons –> increases muscle strength

Question 12

when should cholinesterase inhibitors be given?

Answer 12

give 30-45 minutes prior to eating to strengthen swallowing muscles

Question 13

example of cholinesterase inhibitor

Answer 13

neostigmine (Prostigmin)

Question 14

MOA of neostigmine

Answer 14

–enhances cholinergic action by facilitating transmission of impulses across neuromuscular junctions
–in therapeutic doses, affects muscarinic and nicotinic receptors

Question 15

effect of cholinergics on GI tract

Answer 15

–increased motility
–diarrhea

Question 16

effect of anticholinergics on GI tract

Answer 16

–decreased motility
–constipation

Question 17

effect of cholinergics on mouth

Answer 17

increased secretions

Question 18

effect of anticholinergics on mouth

Answer 18

dry mouth

Question 19

effect of cholinergics on bladder

Answer 19

urinary urgency

Question 20

effect of anticholinergics on bladder

Answer 20

urinary retentione

Question 21

effect of cholinergics on heart

Answer 21

bradycardia

Question 22

effect of anticholinergics on heart

Answer 22

tachycardia

Question 23

effect of cholinergics on lungs

Answer 23

bronchial constriction

Question 24

effect of anticholinergics on lungs

Answer 24

bronchodilation

Question 25

effect of cholinergics on eyes

Answer 25

miosis (constriction)

Question 26

effect of anticholinergics on eyes

Answer 26

mydriasis (dilation)

Question 27

neostigmine adverse effects (muscarinic)

Answer 27

--increased secretions, GI motility --urinary urgency --bradycardia --bronchial constriction --miosis, near-sightedness

Question 28

neostigmine adverse effects (neuromuscular/nicotinic)

Answer 28

--therapeutic doses = increased muscle contraction --toxic doses = reduced contraction --toxicity --> cholinergic crisis

Question 29

cholinergic crisis

Answer 29

--extreme muscle weakness or paralysis --s/s of muscarinic stimulation

Question 30

treatment for cholinergic crisis

Answer 30

--mechanical ventilation --antidote for muscarinic symptoms = atropine

Question 31

what should the MG patient wear at all time?

Answer 31

med alert bracelet

Question 32

MG crisis vs. cholinergic crisis

Answer 32

MG crisis --not enough stimulation or acetylcholine --muscles are not stimulated and weak --leads to respiratory failure Cholinergic crisis --too much acetylcholine or nystigmine --overstimulation of muscles and muscles are worn out --leads to respiratory failure

Question 33

how to differentiate between MG or cholinergic crisis?

Answer 33

--give EDROPHONIUM --if they improve = MG crisis because increase in acetylcholine --if they worsen = cholinergic crisis because too much acetylcholine

Question 34

edrophonium

Answer 34

short acting cholinesterase inhibitor that increases acetylcholine temporarily