Parkinson's

Question 1

What is Parkinson’s characterised by?

Answer 1

Loss of dopaminergic neurons in the substantia nigra, the region of the brain responsible for modulating motor movement and reward functions, as well as being involved in dopamine production.

Question 2

What are the common symptoms of Parkinson’s?

Answer 2

Tremors
Stiffness
Slowness
Balance issues

Question 3

What is first line treatment of Parkinson’s?

Answer 3

Levodopa

Question 4

How does levodopa work?

Answer 4

Crosses blood brain barrier and acts as a dopamine precursor in the presynaptic terminals of dopaminergic neurons, resulting in decarboxylation to form dopamine.

Question 5

What are “on-off” periods in levodopa and other Parkinson’s treatment?

Answer 5

Diphasic dyskinesia - 2 “off” periods of erratic movements, first when levodopa is first given and when it wears off.

Question 6

What can be done to improve end-of-dose deterioration and on-off periods?

Answer 6

Change timing of doses
Increase the dose
Add in other medicines

Question 7

What is a key complication of levodopa?

Answer 7

Dopamine dysregulation syndrome - impulse control disorders such as pathological gambling, binge eating, and hypersexuality.

Question 8

What is levodopa often combined with?

Answer 8

Dopa decarboxylase inhibitors such as:
Benserazide (co-beneldopa)
Carbidopa (co-careldopa)

Question 9

How do dopa decarboxylase inhibitors work?

Answer 9

They inhibit aromatic amino acid decarboxylase (AAAD) outside the brain to prevent premature decarboxylation of levodopa to dopamine before it penetrates the BBB.

Question 10

What are some of the main side effects caused by levodopa?

Answer 10

Nausea and vomiting
Hypotension
Anxiety and depression
Hallucinations (mainly with changes in dose)

Question 11

How do dopa decarboxylase inhibitors reduce nausea and vomiting caused by levodopa?

Answer 11

Premature decarboxylation of levodopa to dopamine can result in activation of dopamine receptors in the gut and therefore nausea and vomiting. These medicines prevent this premature decarboxylation.

Question 12

How should a patient be transferred from one levodopa/dopa-decarboxylase inhibitor preparation to another?

Answer 12

Discontinue previous preparation 12 hours before starting next one. Avoid abrupt withdrawal due to risk of neuroleptic malignant syndrome and rhabdomyolysis (muscle break down).

Question 13

How do dopamine agonists work?

Answer 13

Mimic dopamine by selectively stimulating D2 receptors in the brain.

Question 14

Why are dopamine receptor agonists second-line to levodopa?

Answer 14

They are less effective at improving motor symptoms and the ability to do day-to-day tasks and they have an increased risk of hallucinations.

Question 15

What are the 2 types of dopamine agonists?

Answer 15

Ergot - bromocriptine, pergolide, cabergoline. Associated with increased risk of heart and lung problems.
Non-ergot - ropinirole, rotigotine, apomorphine. Newer and safer.

Question 16

How do COMT inhibitors work?

Answer 16

Inhibit catechol-O-methyl transferase (COMT) to prevent peripheral breakdown of levodopa, allowing more of it to reach the brain.

Question 17

When would a COMT inhibitor be prescribed?

Answer 17

As an adjunct treatment with levodopa if a patient develops dyskinesia or motor fluctuations.

Question 18

Name 1 COMT inhibitor.

Answer 18

Entacapone.

Question 19

How do MAO-B inhibitors work?

Answer 19

Inhibit monoamine oxidase B (MAO-B) to prevent removal of “excess” dopamine from the brain.

Question 20

Name 3 MAO-B inhibitors.

Answer 20

Safinamide
Isocarboxazid
Phenelzine

Question 21

When would a MAO-B inhibitor be prescribed?

Answer 21

As an adjunct treatment with levodopa if a patient develops dyskinesia or motor fluctuations.

Question 22

Why would an anti-emetic be prescribed to a Parkinson’s patient?

Answer 22

Many antiparkinson’s medication, such as levodopa, can cause nausea and vomiting due to stimulation of dopamine receptors in the gut.

Question 23

What anti-emetics could you prescribe to a Parkinson’s patient?

Answer 23

Low dose domperidone (10mg tds) for maximum 1 week (stop when nausea resolves).

Question 24

How does domperidone work?

Answer 24

Dopamine D2 receptor antagonist which works by:
1. inhibiting dopamine receptors involved in emesis in the chemoreceptor trigger zone
2. inhibiting dopamine receptors in the gut to prevent dopamine slowing gastric motility (causes nausea and vomiting) i.e., speeds up gastric motility

Question 25

What is a common side effect of domperidone?

Answer 25

Dry mouth

Question 26

What anti-emetics cannot be used in Parkinson’s and why?

Answer 26

Metoclopramide and prochlorperazine.
They are dopamine antagonists, same as domperidone, but they cross the BBB at a much higher rate where they can cause extrapyramidal side effects, even in those without Parkinson’s.

Question 27

What are critical medicines?

Answer 27

Ones that cannot be easily be replaced by other medicines and if it is omitted it could cause serious harm to the patient.

Question 28

Why are anti-Parkinson’s medicines considered critical medicines?

Answer 28

Parkinson’s medicines are extremely time critical due to end-of-dose deterioration and on-off periods. If a dose is late or missed the patient will start to experience Parkinson’s symptoms e.g., tremor, confusion, agitation, difficulty communicating.

Question 29

What should you recommend if a person forgets to take their Parkinson’s medication?

Answer 29

Take it as soon as they remember and adjust the subsequent doses that day. Do not take 2 doses together.

Question 30

Why are swallowing issues common in Parkinson’s?

Answer 30

Swallowing can be affected by rigidity of muscles in the face, jaw, and tongue.

Question 31

What solutions are there to swallowing difficulties?

Answer 31

Adjust patients position and head posture.
Take smaller bites when eating
Change diet to softer foods and thicker drinks.
Use an enteral feeding tube.

Question 32

How can Parkinson’s medication be given via enteral feeding tube

Answer 32

Co-beneldopa - dispersible tablets available
Co-careldopa - regular tablets can be dispersed in 10ml of water.
Entacapone - regular tablets can be dispersed in 10ml of water.
Ropinirole - regular tablets can be dispersed in 10ml of water.
Domperidone - regular tablets can be dispersed in 10ml of water. Also available as suspension and suppository.