Parkinson’s
Pathophysiology of Parkinson’s
chronic progressive neurodegenerative disease
loss of dopamine neurons in the nigrostriatal pathway
50-80% neurons lost before symptoms present
presence of Lewy bodies in those neurons
o clumps of proteins e.g. alpha synuclein
o this is found primarily in the brain
o these proteins can build up leading to dysfunction
changes to GABA glutamate pathway may contribute to non-motor and axial
symptoms
o axial: freezing, postural instability etc
Risk factors
genetic factors
exposure to neurotoxins
head injury/brain injury
Motor Symptoms
bradykinesia: slowness in initiating voluntary movement, or repetitive actions
hypokinesia: reduced facial expressions, difficulty with fine movements
tremor
o coarse tremor
o pill rolling tremor
rigidity
o moves through the nigrostriatal pathway to the nasal ganglia
o to control smooth movements
o damage and death of dopamine neurons in the nigrostriatal pathway will
cause rigidity
Non-Motor Symptoms
micrographia
o abnormally small, cramped handwriting
swallowing and speech problems
drooling
loss of smell
excessive sweating
depression
memory problems
sleep disturbance
constipation
dizziness and falls
urinary problems
dementia
Aims for drug treatments for Parkinson’s
only started when motor symptoms affect a patient’s ability to function
aim is to increase dopamine levels in the brain
treat symptoms only
not curative or disease modifying (progression not affected)
, treatments for non-motor symptoms
o symptomatic
o e.g., constipation → laxatives
Drugs used for motor symptoms
BNF!!!!!
levodopa
MAO-B inhibitors
dopamine agonists
COMT inhibitors
amantadine
anticholinergics
Treatment pathway for first-line therapy failure
disease is progressing
add a dopamine agonist and levodopa
then add a COMT inhibitor
amantadine or antimuscarinic for dyskinesia
or if really advanced add an advanced therapy
What is levodopa?
combined with dopa-decarboxylase inhibitor
always!: CO-CARBEDOPA
will not do anything if given alone
most effective treatment
treats motor symptoms of tremor, bradykinesia and rigidity
MOA levodopa
also known as L-DOPA
crosses the blood brain barrier via LAT1 on endothelial cells
is decarboxylated to form dopamine
by DOPA decarboxylase
This supplemental dopamine performs the role that endogenous dopamine cannot
due to a decrease of natural concentrations and stimulates dopaminergic receptors
Advice for prescribing levodopa
low dose titrated up to limit side effects of
o postural hypotension
o nausea
o vomiting
o psychiatric effect
initiate when symptoms interfere with daily activities
until then use other first line therapies
o due to long term problems of levodopa
o decreased efficacy over time
o causes dyskinesias earlier in the disease (involuntary movements)
o but this is being looked at and not confirmed
protein can alter its absorption
o so maybe space away from food to increase absorption
o or ask patient to have a low protein diet
What are MAO-B inhibitors?
selegiline and rasagiline
Pathophysiology of Parkinson’s
chronic progressive neurodegenerative disease
loss of dopamine neurons in the nigrostriatal pathway
50-80% neurons lost before symptoms present
presence of Lewy bodies in those neurons
o clumps of proteins e.g. alpha synuclein
o this is found primarily in the brain
o these proteins can build up leading to dysfunction
changes to GABA glutamate pathway may contribute to non-motor and axial
symptoms
o axial: freezing, postural instability etc
Risk factors
genetic factors
exposure to neurotoxins
head injury/brain injury
Motor Symptoms
bradykinesia: slowness in initiating voluntary movement, or repetitive actions
hypokinesia: reduced facial expressions, difficulty with fine movements
tremor
o coarse tremor
o pill rolling tremor
rigidity
o moves through the nigrostriatal pathway to the nasal ganglia
o to control smooth movements
o damage and death of dopamine neurons in the nigrostriatal pathway will
cause rigidity
Non-Motor Symptoms
micrographia
o abnormally small, cramped handwriting
swallowing and speech problems
drooling
loss of smell
excessive sweating
depression
memory problems
sleep disturbance
constipation
dizziness and falls
urinary problems
dementia
Aims for drug treatments for Parkinson’s
only started when motor symptoms affect a patient’s ability to function
aim is to increase dopamine levels in the brain
treat symptoms only
not curative or disease modifying (progression not affected)
, treatments for non-motor symptoms
o symptomatic
o e.g., constipation → laxatives
Drugs used for motor symptoms
BNF!!!!!
levodopa
MAO-B inhibitors
dopamine agonists
COMT inhibitors
amantadine
anticholinergics
Treatment pathway for first-line therapy failure
disease is progressing
add a dopamine agonist and levodopa
then add a COMT inhibitor
amantadine or antimuscarinic for dyskinesia
or if really advanced add an advanced therapy
What is levodopa?
combined with dopa-decarboxylase inhibitor
always!: CO-CARBEDOPA
will not do anything if given alone
most effective treatment
treats motor symptoms of tremor, bradykinesia and rigidity
MOA levodopa
also known as L-DOPA
crosses the blood brain barrier via LAT1 on endothelial cells
is decarboxylated to form dopamine
by DOPA decarboxylase
This supplemental dopamine performs the role that endogenous dopamine cannot
due to a decrease of natural concentrations and stimulates dopaminergic receptors
Advice for prescribing levodopa
low dose titrated up to limit side effects of
o postural hypotension
o nausea
o vomiting
o psychiatric effect
initiate when symptoms interfere with daily activities
until then use other first line therapies
o due to long term problems of levodopa
o decreased efficacy over time
o causes dyskinesias earlier in the disease (involuntary movements)
o but this is being looked at and not confirmed
protein can alter its absorption
o so maybe space away from food to increase absorption
o or ask patient to have a low protein diet
What are MAO-B inhibitors?
selegiline and rasagiline
