The main aim of pharmacological interventions is to increase the level of available dopamine. The most common medication used to treat Parkinson's is levodopa which is available in the forms of Sinemet and Madopar. Levodopa will not arrest the progression of Parkinson's but will reduce the symptoms of stiffness and slowness.
As Parkinson's affects each person differently it is important to individually tailor medication regimens accordingly. Education on the topic of medication should include; what the medication is for, what benefits should be expected, possible side effects and their management, drug interactions and how to keep an accurate record so information can be given to the doctor at each visit.
It is relatively common for people to require higher doses of medication and therefore experience side effects as the illness progresses and dopamine production is reduced. It is believed by some that levodopa will provide maximum benefit for a period of 5 - 10 years, although people have reported successful treatment for over 20 years.
After this period the dilemma of balancing the therapeutic benefits as opposed to possible side effects become more difficult. The objective is to obtain maximum mobility with minimal side effects. Other factors such as diet need to be considered when taking levodopa. It is advisable to take levodopa on an empty stomach as a diet high in protein may decrease the absorption rate of this medication. However, if nausea and vomiting occur, taking this medication with food may be the best option.
It is extremely important to gain the maximum benefit from medication while keeping side effects to a minimum. Medication must be given at the correct dosage time to allow for absorption time and the attainment of therapeutic levels. Most people respond well to education about medication and are able to evaluate the effectiveness of their own medication regimes. It is important that they understand the factors which can negatively influence the effectiveness of medication and how to minimise these.
Stress is one of the major factors influencing mobility and thus effectiveness of pharmacological interventions.
- More dopamine/medication is required as the illness progresses, therefore side effects are likely
- Levodopa alleviates symptoms but does not cure Parkinson's
- Medication regimes must be individually tailored
- Education about medication is vital
1. Levodopa - Sinemet, Madopar
- converted into dopamine; reduces rigidity and bradykinesia.
Possible Side Effects:
- nausea and vomiting (use domperidone)
- constipation (diet and laxative)
- hypotension (postural changes)
- increased lethargy (activity/rest programme)
2. Dopamine Agonists
- Permax (Pergolide), Parlodel (bromocriptine), Apomorphine. Cabergoline, Ropinerole, Pramipexole (trial stage)
- used as adjuncts to levodopa; stimulates the brain directly by mimicking dopamine.
Possible Side Effects:
- may potentiate side effects as listed above.
3. Monoamine oxidase type B inhibitor
- Selegiline (eldepryl)
- prevents the metabolism of dopamine within the brain
- may have neuroprotective properties (controversial)
- currently used in early stagesPossible
- may potentiate the side effects as listed above
- Artane (benzhexol), Cogentin, (benztropine) and others
- reduce levels of acetylcholine in the brain
- mild anti parkinsonian effect, more effective for tremorPossible
- dry mouth, blurred vision, constipation, urinary hesitancy and retention
- mental confusion, decreased memory and hallucinations
Potential Long Term Side Effects:
Approximately 50% of patients on levodopa treatment develop delayed side effects after approx 5 - 10 years. These vary greatly in severity from person to person. Abnormal and involuntary movements:
Twisting and dancing movements of the arms, legs and trunk (dyskinesias) and unusual muscle contractures or cramps, especially in the foot (dystonia)
A tendency for the benefits of each individual dose of medication to wear off in a predictable manner before the next is scheduled to be taken
Unpredictable fluctuations in motor function, not clearly associated with the taking of medications
5. COMT Inhibitors Comtan (Entacapone), Tasmar (Tolcapone)
- Used in conjunction with levodopa preparations
- Blocks an enzyme, known as COMT, to prevent the breakdown of levodopa in the intestinal tract
Possible side effects:
Nausea and Vomiting ; Diarrhoea or Constipation
Dry Mouth Increased Lethargy Depression