Movement Disorders

Question 1

Describe how L Dopa works

What are Its advantages and disadvantages

Answer 1

Taken up by dopaminergic cells in substantia nigra & converted to dopamine
(Dopamine cant cross blood brain barrier directly)
E.g. Sinemet, Madopar
Poorly absorbed (90% inactivated in intestinal wall)
Short half life so fluctuations in symptoms
Advantages: highly efficacious, few side effects (e.g. Nausea and vomiting, hypotension)
Disadvantages: may loose efficacy over time, causes involuntary movements & motor complications

Question 2

Describe how dopamine receptor agonists work

What are its advantages and disadvantages

Answer 2

Bind to dopamine receptor agonists directly

Advantages: Newer, non-ergot derived drugs have fewer side effects, direct acting, less motor complications, possible neuroprotective role

Disadvantages: less effective than L dopa, impulse control disorders, psychiatric side effects, expensive

Question 3

Describe how monoamine oxidase B inhibitors work

Answer 3

Inhibits this enzyme that metabolises dopamine

Can be used alongside L dopa to enhance effects

Question 4

What is the effects of COMT Inhibitors

Answer 4

Reduces peripheral breakdown ofL dopa
No therapeutic effect alone
Nut can prolong response of L dopa

Question 5

Describe how anticholinergics work

Answer 5

Ach may have Antagonistic effect to dopamine
Minor role in parkinsons - treat tremor but no effect on bradykinesia
Side effects: confusion, drowsiness, anti-cholinergic effects (e.g. Dry mouth, urinary retention)

Question 6

How is Myasthenia Gravis mainly treated

Answer 6

Acetylcholinesterase inhibitors:
Enhance neurotransmitter transmission
But excess dose can cause depolarising block (cholinergic crisis: flaccid paralysis, resp failure)

Question 7

What are the main classes of drugs used to treat Idiopathic Parkinson’s Disease

Answer 7

Levodopa (L-Dopa)
Dopamine receptor agonists
Monoamine Oxidase B Inhibitors

COMT inhibitors
Anticholinergics