Parkinson's Pharmacology

Question 1

What is the first line Tx in Parkinson’s?

Answer 1

Levodopa is the first Line for PD, and is used in combination with Carbidopa (decarboxylase inhibitor)

Question 1

Why is Carbidopa given with levodopa?

Answer 1

Inhibits breakdown of levodopa in peripheral tissue (outside the Blood Brain Barrier).

Question 2

What are some of the adverse effects?

Answer 2

Nausea, vomiting
Postural Hypotension
Tachycardia.

Question 3

Domperidone is preferred over metoclopramide as an antiemetic to treat Levodopa - induced nausea and vomiting because..?

Answer 3

Domperidone does not cross the Blood Brain Barrier.

Vomiting centre is outside the BBB.

Question 4

What are some slowly developing effects with Levodopa?

Answer 4

Motor complications, including Response fluctuations - “wearing off”.

The “On-Off effect”
Dyskinesia’s

Question 5

Lost a disproportionate amount of money in online betting. Which could be the offending medication?

Answer 5

Rotigotine (Dopamine Agonist)

• Causes a dysregulation of the reward pathway.

Question 6

Adverse effects of Dopamine Agonist

Answer 6

• Excessive sleepiness
• Psychosis - Hallucinations / delusions.
• Impulse control disorders

Question 7

When do we prefer Levodopa or Dopamine Agonists in Parkinson’s?

Answer 7

Prefer Levodopa in px > 70 yrs.

Prefer DA’s in px < 70 (unless have any predispositions to adverse effects of DA’s)

Question 8

What are some Central Anticholinergic Drugs?

Answer 8

Orphenadrine, Benzatropine,

Benzatropine used to alleviate Extrapyramidal effect caused by antipsychotic medications.

Question 9

What are some classical features of Parkinson’s?

Answer 9

Asymmetrical

Question 10

What are the features of Drug-Induced Parkinson’s?

Answer 10

• ## Symmetrical

Question 11

What causes Drug-Induced Parkinson’s?

Answer 11

• Anti-psychotics (promethazine, haloparidol)
• Anti-emetics (Procloperazine)

Question 12

Why is drug-induced Parkinson’s not treated with levodopa?

Answer 12

Because receptors are blocked and not available.

Question 13

What happens in Drug-induced Parkinson’s?

Answer 13

Drugs which cause blockage of the domaminergic system (dopamine receptor blockers) mimic the traits of Parkinson’s disease, such as tremors and postural instability.

Question 14

Patients should be advised to take Levodopa with meals to avoid gastric side effects.

Answer 14

Yes.

Question 15

Levodopa causes more daytime sleepiness than Rotigotine.

Answer 15

No, Daytime sleepiness is more common wit DA’s.

Question 16

Patients started on Entacapone should have monthly checks of LFTs due to its hepatotoxic potential.

Answer 16

No, (precursor of Entacapone used to cause this by Entacapone does not)

Question 17

When is Amantadine (Antiviral + Antiparkinsonian drug) for Drug-induced Parkinson’s.

Answer 17

If Anti-cholinergics were contraindicated this would be the next line.

Primarily an antiviral - Also has antiparkinsonian properties

Question 18

What medication can be given in a Parkinson’s Freeze?

Answer 18

Apomorphine (non-selective Dopamine Receptior Agonist)

Parkinsons Freeze - aka Freezing gait, people w parkinsons disease cannot move limbs.

Question 19

GABA agonist, role in spasticity/HD - What drug is this?

Answer 19

Baclofen

Question 20

What Anti-psychotic drug can cause a loss of Parkinson’s control?

Answer 20

Haloperidol - Anti-psychotic medication (blocks Dopamine Receptors - particularly D2 subtype responible for movement)
- can cause Drug induced PD

Question 21

Why are dopamine agonists preferred under 70?

Answer 21

They cause less neurodegeneration than Levodopa and also have less chance of causing The “On-Off” effect.