Parkinson's Drugs

Question 1

List of drugs for Parkinson’s Disease

Answer 1

Dopamine Agonists
1. Levodopa/Benserazide
2. Levodopa/Carbidopa

Ergot-derived Dopamine Agonists: Bromocriptine

Non-ergot derived Dopamine Agonists:
1. Ropinirole
2. Pramipexole
3. Rotigotine

Irreversible MAO-B Inhibitor:
1. Selegiline
2. Rasagiline

Reversible COMT Inhibitor: Entacapone

NMDA Antagonist: Amantadine

Other Combination medications: Stalevo (Levodopa, Carbidopa, Entacapone)

Question 1

Levodopa / Carbidopa Formulations used mainly in NUH and Max dosing

Answer 1

250/25 mg Tablet (Credanil)

Max dose: 8 tablets/day (Levodopa 2 g/day, Carbidopa 200 mg/day)

Question 2

Levodopa/Benserazide Formulations used mainly in NUH

Answer 2

250 mg Tablet (Madopar)

Max dose: Levodopa
- 1200 mg/day for 1st year (6 tabs/day)
- 600 mg/day for subsequent years (3 tabs/day)

Question 3

Counseling points for levodopa: How to take?

Answer 3

1. Empty stomach (But can take with light snacks if irritated)
2. Take on time to maintain the effect of medication
3. Avoid high-protein diet while taking levodopa
4. Other DDIs:
   - Space apart 2 hours: Iron, pyridoxine
   - Alternatives to consider for Metoclopramide, sulpiride

Question 4

Counseling points for levodopa: ADRs?

Answer 4

1. Orange coloration in body fluids (Harmless)
2. Low BP
3. Uncontrolled movement (On-off phenomenon, wearing off effect)
4. Nausea, vomiting

Question 5

What is the role of benserazide and carbidopa?

Answer 5

Prevent peripheral conversion of levodopa in the bloodstream so that more levodopa can enter the brain

This also reduces the side effects of nausea, vomiting

Question 6

Ropinirole formulation and dosing

Answer 6

Form:
- 0.25 mg, 1 mg, 2 mg Tablets
- PR 2 mg, 4 mg Tablet (Requip PD)

IR: 0.25 mg TDS initially, then increase every 7 days
Max: 24 mg/day, 3 divided dose
Usual dose: 12 to 16 mg/day

Question 7

Pramipexole formulation and dosing

Answer 7

Form
- 0.125 mg (Immediate)
- 0.375 mg (Extended)

IR: 0.125 mg TDS increase every 7 days up to 4.5 mg/day
ER: 0.375 mg QD up to 4.5 mg/day

Question 8

Rotigotine Formulation and Dosing

Answer 8

Formulation
2 mg/24 hours
4 mg/24 hours
6 mg/24 hours
8 mg/24 hours

Dosing:
Early stage: Start with 2 mg
Advanced-stage: Start with 4 mg
Do not discontinue abruptly, decrease by 2 mg/24 h EOD

Question 9

Bromocriptine Formulation and Dosing

Answer 9

Form: 2.5 mg Tablet

Dosing:
- Usual PD dose: 1.25 mg BD then 2.5 mg QD in 2-4 week interval
- Absolute max dose: 100 mg/day

Question 10

ADRs of dopamine agonists (ergot/non-ergot)

Answer 10

Dopaminergic:
1. Nausea, vomiting
2. Orthostatic hypotension
3. Leg or arm swelling

Non-dopaminergic:
1. Hallucination, agitation
2. Compulsion (Urges)
3. Sleep attacks (Sudden)

Question 11

MAO-B Inhibitors Place in therapy and dosing

Answer 11

Selegiline 5 mg tablets (Max: 1 tab BD)

Indication:
- PD adjunct
- PD monotherapy in young
- MDD

Rasagiline 1 mg tablets (Max: HALF to 1 tab QD)

Indication:
- PD adjunct
- PD monotherapy

Question 12

What is the special point about selegiline dosing, relating to the ADR?

Answer 12

Take one dose in the morning and one in the afternoon (Liver metabolism to amphetamine causing difficulty sleeping)

Question 13

What are the other ADRs of selegiline and the rationale?

Answer 13

MAO plays a major role in breaking down DA, 5HT, NE and epinephrine

1. Nausea, abdominal pain, constipation, diarrhea (5HT)
2. Low BP (NE)
3. Dry mouth

Rare: Hallucinations

Question 14

Entacapone formulation, place in therapy and dosing

Answer 14

Form: 200 mg Tablet

Indication: PD adjunct to levodopa (increase the effect of levodopa)

Maximum: 1600 mg/day

May need to reduce L-dopa dose

Question 15

ADR to counsel to patients for entacapone

Answer 15

Red-brown urine (harmless)

NVD

Drowsiness

Hallucinations, compulsions

Question 16

DDIs of entacapone

Answer 16

Iron supplements (2h apart)

Some Antidepressants (e.g. Paroxetine, Moclobemide, Venlafaxine)