Describe the pathophysiology of Parkinson’s disease
Progressive reduction of dopamine in the substantia nigra
Describe the aetiology of Parkinson’s disease
Idiopathic
Describe the clinical features of Parkinson’s disease
Core symptoms (usually asymmetrical):
- Resting tremor
- Rigidity
- Bradykinesia
Other symptoms:
- Depression
- Sleep disturbance/insomnia
- Cognitive impairment
Describe the investigation of Parkinson’s disease
- Clinical diagnosis, made by specialist (neurologist)
- Dopamine transporter (DaT) imaging can be used to support the diagnosis (this is rare)
Describe the management of Parkinson’s disease
Does pharmacological therapy alter the natural history of the disease?
Are there any other management options?
Pharmacological therapy does not alter the natural history of the disease, but it does improve motor symptoms:
- Levodopa
- Dopamine agonists
- Monoamine oxidase-B inhibitors
Other management options:
- Physiotherapy
What are the side effects of having too much dopamine (i.e. dose of anti-Parkinson’s medications is too high)?
Dyskinesias:
- Dystonia (excessive muscle contraction)
- Chorea (involuntary jerking movements)
- Athetosis (involuntary twisting/writhing motions, usually in hands and feet)
Give some examples of causes of parkinsonism (other than idiopathic Parkinson’s disease)
“Parkinson’s plus” syndromes:
- Progressive supranuclear palsy (suspect if patient also presents with balance problems and gaze palsy)
- Multiple system atrophy (suspect if patient also presents with autonomic symptoms, e.g. urinary problems, postural hypotension)
- Dementia with Lewy bodies
Iatrogenic:
- Medications, e.g. antipsychotics
Describe the mechanism of action of dopamine agonists and give one example of this class of drug
Stimulate dopamine receptors in the basal ganglia (they mimic dopamine)
Ropinirole
Give 2 potential side effects of dopamine agonists
- Behavioural changes (loss of inhibition)
2. Pulmonary fibrosis
What is levodopa?
Why must it be combined with another type of drug?
Levodopa = synthetic dopamine
It must be combined with a peripheral decarboxylase inhibitor (e.g. carbidopa or benserazide) to stop it from being broken down in the body before it is able to cross the blood-brain barrier
What is the name of the drug containing levodopa and carbidopa?
Co-careldopa
What is the name of the drug containing levodopa and benserazide?
Co-benyldopa
Describe the mechanism of action of monoamine oxidase-B inhibitors
Give 2 examples of drugs belonging to this class
Inhibit monoamine oxidase-B enzyme, which breaks down dopamine
Rasagiline, selegiline
Which antiemetic is considered SAFE to use in Parkinson’s disease?
Why is this?
Domperidone
This is a dopamine antagonist BUT it does not easily cross the blood-brain barrier, and so the risk of developing EPSEs is minimal
