Parkinson's disease drugs

Question 1

Causes of Parkinsonism

Answer 1

Parkinson’s disease
Antipsychotics
Vascular - mainly affecting pons
Progressive supranuclear palsy - eye movement disorders and truncal rigidity
Multiple systems atrophy - severe autonomic dysfunction
Corticobasal degeneration

Question 2

What does a DAT scan show

Answer 2

Presynaptic dopamine uptake

Question 3

MoA of levidopa

Answer 3

Crosses BBB to enter CNS and converted to dopamine

Taken up by dopaminergic neurones in substantia nigra (degenerated in disease so variable effects)

Question 4

How much levidopa enters CNS

Answer 4

<1%

Question 5

What must be given with levidopa and why

Answer 5

Peripheral DOPA decarboxylase inhibitor e.g Co-careldopa
Or
Catechol-O-methyl transferase inhibitor e.g entacapone
To increase CNS uptake of levidopa and reduce side effects

Question 6

Benefits of levidopa

Answer 6

Efficacious

Low risk of side effects

Question 7

Disadvantages of levidopa

Answer 7

Motor symptoms fluctuate as blood level fluctuate
Efficacy decreases over time
Involuntary movements

Question 8

Drug interactions of levidopa

Answer 8

Vitamin B6 increases peripheral levidopa breakdown
Antipsychotics block dopamine receptors
MAOIs - increased risk of hypertensive crisis

Question 9

Examples of tablet forms of dopamine agonist

Answer 9

Ropinirole

Pramipexole

Question 10

Example of patch form of dopamine agonist

Answer 10

Rotigitine

Question 11

Advantages of dopamine agonists

Answer 11

Less dyskinesia

Question 12

Disadvantages of dopamine agonists

Answer 12

Not as efficacious as levidopa
Impulse control/reward system dysfunction
More psychiatric side effects (dose limiting)

Question 13

Side effects of dopamine agonist

Answer 13

Sedation
Hypotension
Nausea
Hallucinations
Confusion

Question 14

Examples of monoamine oxidase B inhibitors

Answer 14

Selegiline

Rasagaline

Question 15

MoA of MOAIs in Parkinson’s disease and when are they indicated

Answer 15

Decrease dopamine breakdown in brain

Used to prolong action of levidopa if having motor fluctuations

Question 16

Anticholinergics for Parkinson’s disease

Answer 16

Procyclidine

Orphenadrine

Question 17

Indication of anti cholinergics in Parkinson’s disease

Answer 17

To treat tremor

Question 18

Disadvantages of anticholinergics

Answer 18

Constipation
Dry mouth
Drowsiness
Confusion
Has no effect on bradykinesia

Question 19

Describe amantadine

Answer 19

MoA unknown
Poor efficacy
Little effect on tremor
Few side effects

Question 20

Who is suitable for Parkinson’s disease surgery

Answer 20

Dopamine responsive
Significant side effects with levidopa
No psychiatric illness

Question 21

What surgery is an option for Parkinson’s disease

Answer 21

Deep brain stimulation of subthalamic nucleus

Question 22

Describe myasthenia gravis

Answer 22

Fatiguable skeletal muscle weakness (extraocular, bulbar, proximal limb, resp)
Autoimmune antibodies against motor end plate nicotinic receptors

Question 23

How can you test for myasthenia gravis

Answer 23

Ask patient to look up

Eyelids start to droop while eyebrows still raised

Question 24

What drugs can exacerbate myasthenia gravis and cause myasthenic crisis

Answer 24

Beta blockers
ACEi
Aminoglycosides

Question 25

Management of myasthenic crisis

Answer 25

Protect airways! - may need to intubate
Acetylcholinesterase inhibitors
Plasmapheresis/corticosteroids