Drug Treatments
There is no cure for Parkinson's, drugs are used to:
"It is not possible to idnetify a universal first chchoice drug therapy for people with early PD. The choice of drug first prescribed should take into account:
Levodopa
Levadopa works by restoring some dopamine back to the brain.
Levidopa has been the standard drug for dealing with the effects of Parkinson's for the last thirty years. It is normally combined with either carbidopa or besnerazide which help the levodopa to cross the blood-brain barrier.
Side-effects of levodopa can include nausea, infection, hypertonia and headache. Prolonged use of levodopia can cause problems with motor function in the form of unwanted and involuntary movements.
Dopamine Agonists
Dopamine agonists work by mimicking the effect of dopamine by binding directly with the post-synapptic dopamine receptors in the brain. They have mostly been used with levodopa but are now being considered to for use by themselves and thus delaying the motor complications that come with levodopa. The NICE guidance lists the following as adverse effects of taking dopamine agonists:
The NICE guidance warns doctors not to use ergot-derived dopamine agonists as these are known to have serious side effects in some cases. The guidance also points out the need for further research into the effects of dopamine agonists on older people.
MAOB inhibitors
Monoaomine oxidase type B is responsible for breaking down dopamine in the brain. MOAB inhibitors work by blocking this action. They are usually prescribed alongside levodopa but can also be precribed by themselves during the earliest phases of the disease. The NICE guidance says; "the trial evidence supports the ability of MAOB inhibitors in PD to improve motor symptoms, improve activities of daily living and delay the need for levodopa." There are two MAO-B inhibitors available in the UK - selegiline and rasgiline. When taken on its own, selegiline has very few side effects, when taken alongside levodopa side effects can include:
Rasigiline has the following side effects when taken on its own:
Rasigiline when taken with levodopa can increase uncontrolled movements and the number of falls.
COMT Inhibitors.
Catechol-O-methyl transferase inhibitors work by helping to increase the amount of levodopa that crosses into the brain.
Two COMT inhibitors are available in the UK, entacapone and tolcapone. Entacapopne is also available as a triple combination with levodopa and carbidopa (Stalevo).
Side effects with COMT inhibitors are nausea, diarrhoea, aggravated parkinsonism and constipation.
Because of previous serious adverse effects tolcapone can only be given to people who have failed to respond to entacapone.
The NICE guidance recommends the people in the later stages of Parkinson's should be offered a "triple combination preparation of levodopa, carbidopa and entacapone."
Amantadine
Amanatadine has been used in the past for the treatment of people in the early stages of the disease but has now fallen into disuse with the advent of levodopa and carbidopa. It has however been shown to be effective in reducing dyskinesia (difficulty or distortion in performing voluntary movements) in people who are in the later stages of Parkinson's.
Side effects include swelling of the ankles, a mottled appearance on the skin of the lower leg and confusion.
Surgical procedures
Subthalamic nucleus - deep brain stimulation
Stimulation, by means of an elctrode fitted inside the skull, of the subthalmic nucleus has been shown to improve Parkinsonian symptoms, emotional and social functioning. In this procudure the level of stimulation is controlled by a pulse generator which is placed in the chest wall. The patient thus has a degree of control over the stimulator.
There is some concern about the incidence of suicide attempts in people who have had this operation, there is also small but "significant" risk of permanent neurological disability.
The NICE Guidance states that bilateral STN stimulation may be used in people with Parkinson's Disease who:
The same guidance applies to Globus pallidus interna (GPI) stimulation, as do the concerns about adverse events and cost.
Thalamic Stimulation
Thalamic deep brain stimulation is only recommended for those people who predominantly have severe disabling tremor and where STN stimulation cannot be performed.
