L Dopa/ Peripheral Decarboxylase Inhibitor

Question 1

Name two common L Dopa/ Peipheral Decarboxylase Inhbirots?

Answer 1

Sinemet and Madopar

Question 2

What is Sinemet made up from?

Answer 2

Levo Dopa and Carbidopa

Question 3

What is Madopar bade up of?

Answer 3

Levo Dopa and Benserazide

Question 4

What is the pathology behind Parkinson’s?

Answer 4

Lack of dopamine in the niagastriatal pathway. This is the pathway between the substantial nigira (midbrain) to the Corpus Striatum (basal ganglia). This lack of dopamine causes the basal ganglia to have a greater inhibitory input to the thalamus and reduced the excitatory input to the midbrain.
= Parkinsons

Question 5

Name some common features of Parkinson?

Answer 5

Bradykinesia and Rigidity

Question 6

How does Levo Dopa work?

Answer 6

Levo dopa is a precursor to dopamine. It is broken down to dopamine by the enzyme dopa decarboxylase.

Question 7

What enzyme is responsible for the breakdown of levo dopa to dopamine?

Answer 7

Dopa decarboxylase

Question 8

Why can’t you give dopamine as the treatment for Parkinson’s?

Answer 8

Cannot pass the BBB

Question 9

How do you stop Levo Dopa being broken down before it crosses the BBB?

Answer 9

Give it with a peripheral decarboxylase inhibitor e.g. carbidopa and bensarazide

Question 10

What are dopamine agonists used for? and examples

Answer 10

Often given before treatment with levo dopa

Ropinirole and pramipexol - selective agonists for the D2 receptor, which predominates in the striatum.

Question 11

What are the common indications for using Levodopa?

Answer 11

1. Early Parkinson’s: dopamine agonists usually preferred
2. Late Parkinson’s
3. Idiopathic Parkinson’s: e.g. parkinsoninism linked to other drugs not idiopathic

Question 12

What are the contra-indications for using Levodopa?

Answer 12

Pregnancy

Question 13

When should Levodopa be used with caution

Answer 13

Elderly
Psyciatric disorders
Cognitive disorders e.g. Alzheimers as can aggravate confusion and hallucinations
CV disease as can cause hypotension and arrhythmias

Question 14

What are the common interactions with Levo dopa?

Answer 14

Blood pressure medications (aggravates low bp)
Metoclopramide (opposite dopamine effects)
Antipsychotics (opposite dopamine effects)
Monoamine oxidase inhibitors (risk of hypertension crisis)

Question 15

What are the side effects of Levodopa?

Answer 15

Nausea
Confusion/Drowsiness
Hypotension
Hallucinations
Wearing off effect

Question 16

What is the wearing off effect?

Answer 16

Patients symptoms worsen towards the end of a dosage interval
Gets worse the longer a patient has been on the treatment

Question 17

How can you overcome the wearing off effect?

Answer 17

Increasing the dose and frequency of the medication but this can generate the opposite effects causing involuntary movements (dyskinesias) at the beginning of the dosage interval

Question 18

What is the on-off effect?

Answer 18

Going from worsening symptoms of bradykikesias and rigidity at the end of a treatment cycle to the opposite effects e.g. dyskinesias at the beginning of the next cycle.

Question 19

Why should levodopa never be stopped suddenly?

Answer 19

There is a deterioration in symptoms and the risk of neuroleptic malignant syndrome

Question 20

What is neuroleptic malignant syndrome?

Answer 20

A side effect of suddenly coming of levodopa causing life-threatening:

• fever
• altered mental status
• muscle rigidity
• autonomic dysfunction

Question 21

What is a side effect of dopamine present outside the BBB?

Answer 21

Nausea