Msk 12

Question 1

Binding of released ACh to ______ receptors depolarizes the motor end-plate.

Answer 1

Nicotinic

Question 2

Binding of _____ to LRP4, and_______ complex, clusters AChR at the NMJ.

Answer 2

Agrin

Muscle Specific Tyrosine Kinase (MuSK)

Question 3

Myasthenia gravis results from autoantibodies to _____, ______, or ________.

Answer 3

AChR

MuSK

LRP4

Question 4

What are the two reversible AChE inhibitors?

Answer 4

Edrophonium & Ambenonium

Question 5

What are the 3 slowly reversible inhibitors of AChE?

Answer 5

Neostigmine (Prostigmin®)

Pyridostigmine (Mestinon®)

Physostigmine

Question 6

What is the general type of inhibitor used for cholinesterase inhibition?

Answer 6

Carbamate inhibitors

Question 7

What are the trade names for Edrophoinium, a drug used as a diagnostic agent in myasthenia gravis?

Why is it used as a diagnostic agent?

Answer 7

Tensilon

Enlon

Short duration of action (5-15 min)

Question 8

What are the 3 drugs used to treat Myasthenia Gravis?

Answer 8

Pyridostigmine

Neostigmine

Ambenonium

Question 9

Increased ACh levels in autonomic synapses activates ________ receptors.

What can be done to block this?

Answer 9

Muscarinic

Causes:

Bradycardia

Increased GI motility

Salivation

Miosis

Administer atropine with the carbamate inhibitor

Question 10

What is the most often used inhibitor for Myasthenia Gravis?

Answer 10

Pyridostigmine (3-6 hours)

Question 11

What are the two aminopyridines that block voltage-dependent K⁺ channels at the neuromuscular jxn?

Answer 11

Dalfampridine

 - 4-aminopyridine
 - Ampyra®

3,4-diaminopyridine

Question 12

How do aminopyridines work?

Answer 12

Blocking K⁺ channels enhances Ach release at the synapse

Keeps the endplate depolarized longer

Question 13

What are aminopyridines used to treat?

Answer 13

Lambert-Eaton Myasthenic Syndrome

Question 14

How do we treat the autoimmune component of myasthenic diseases?

Answer 14

Glucocorticoids - Prednisone (Deltasone®)

Azathioprine (Imuran®)

Question 15

In the treatment of myasthenic diseases, how do glucocorticoids work?

Answer 15

Steroid receptor activation –> reduced phagocytic cell migration to sites such as NMJ

Decreases antigen-presenting fxn of phagocytic cells

High doses can reduce antibody production

Question 16

For a patient complaining of muscle weakness but already receiving drug therapy to manage her Myasthenia Gravis, how can we determine if she is taking an inadequate dosage or if she is overdosing?

Answer 16

Administer Tensilon test

Inadequate dosage = immediate improvement in muscle strength

Overdose = no effect or symptoms worsen

Question 17

Name some adverse effects related to glucocorticoid treatment.

Answer 17

Moon facies

weight gain

muscle wasting

hyperglycemia

osteoporosis

hypokalemia

hypertension

infections

Question 18

How does Azathioprine (Imuran®) work?

Answer 18

Azathioprine converted to 6-mercaptopurine

6-mercaptopurine blocks de novo purine synthesis in lymphocytes to prevent T cell proliferation during antigen challenge

Question 19

What are some adverse effects of Azathioprine?

Answer 19

Affects rapidly growing cells (e.g. bone marrow, GI tract)

Leukopenia, thrombocytopenia

NVD

Increased risk of infections, neoplasias

Additive with other myelosuppressive agents