Step one: pre-consultation
Step one: pre-consultation
There are some communication issues to bear in mind. The speech of a person with PD is often slurred and facial hypokinesia (reduction in spontaneous and emotional facial expressions) is common.
Patients with PD may take slightly longer to initiate speech and lack facial expression when talking to you. Their voice is often monotone. They can also experience dyskinesias (involuntary muscle movements such as jerking, twitches or spasms), which can affect any part of the body including the face.
Cognition issues can be an effect from both PD itself and the medications used to treat it. Slowness of thought is quite common so, when asking a question, remember that the person may respond more slowly than you are expecting.
The three main medications
All current PD medications are for symptom management as none have yet been proven to have disease modifying or neuroprotective properties. As PD is an incurable progressive condition, the aim of treatment is to control the symptoms and improve patients’ quality of life.
Explaining the medications:
Levodopa is a precursor to dopamine, usually given with a DOPA decarboxylase inhibitor (benserazide hydrochloride or carbidopa) as co-beneldopa or co-careldopa. The DOPA decarboxylase inhibitor blocks the peripheral conversion of levodopa to dopamine to allow levodopa to cross the blood-brain barrier and then be converted to dopamine.
If levodopa is broken down into dopamine in the peripheral system, it activates other dopamine receptors, commonly causing nausea. Domperidone is often the antiemetic of choice prescribed at the start of levodopa therapy.
There are various preparations of levodopa available – immediate/modified release preparations, hard or dispersible capsules, liquids or gels.
Although levodopa is one of the most common and widely used first-line treatments, it is often associated with motor complications, including response fluctuations and dyskinesias:
- Response fluctuations are characterised by large variations in motor performance, with normal function during the ‘on’ period and weakness and restricted mobility during the ‘off’ period
- End-of-dose deterioration with shorter duration of benefit can also occur – modified release preparations may help with this and also with nocturnal immobility
- Hallucinations/delusions, sleep disturbance and nausea are all common side-effects of levodopa and may last throughout treatment or be intermittent. A key aim from the start of treatment is to try to ensure that these side-effects do not negatively impact on adherence.
Dopamine agonists stimulate dopamine receptors both post- and presynaptically and have a similar but less potent effect than levodopa. They are classified as ergot derived (bromocriptine, pergolide and cabergoline) or non-ergot derived (apomorphine, pramipexole, rotigotine and ropinirole). Ergot derived dopamine agonists are often associated with a risk of moderate to severe cardiac valvulopathy and serosal fibrosis, so are not first-line treatments.
For some people, dopamine agonists and the development of compulsive behaviours (addictive gambling and an excessive increased libido) have been linked, especially at high doses. Sudden onset of sleep also occurs more frequently, particularly when the dose is being increased, so patients should be advised to avoid driving and/or operating machinery while the dose is being upped if this side-effect occurs.
MAO-B inhibitors, such as selegiline and rasagiline, prevent the breakdown of dopamine, so have a levodopa-sparing effect. They typically provide less improvement than levodopa in motor symptoms and daily functioning, and can be used in the early stages of the disease as monotherapy or an adjunct to other medications.
If used adjunctly, MAO-B inhibitors help to reduce ‘off’ periods and to extend ‘on’ periods.
Triptans or selective serotonin reuptake inhibitors should not be used concurrently due to the increased risk of potentially fatal serotonin syndrome. When advising on over-the-counter decongestants or cold remedies, people who are on MAO-B inhibitors should be advised to not take medications that contain pseudoephedrine due to the increased risk of hypertensive crisis.
There are also some prescribed medications that people with PD should avoid. Medication that inhibits dopamine receptors could worsen symptoms of the disease. For example, typical antipsychotic medications (e.g. phenothiazines and haloperidol) exacerbate the motor symptoms of PD, as do antiemetics such as prochlorperazine and metoclopramide.