The treatment of Parkinson's disease with dopamine agonists

Parkinson’s disease is a chronic degenerative organic disease with unknown causes. A disappearance of cells with melanin in the substantia nigra is considered as biological artefact of the disease, which causes a degenerative loss of neurons in the corpus striatum of mesencephalon. This structure produces also the transmitter substance dopamine. Due to this disappearance of cells dopamine is not produced in a sufficient quantity which is needed for movement of the body. The questions of this report are concerned the efficiency and safety of a treatment with dopamine agonists. Furthermore the cost-effectiveness is investigated as well as ethic questions. The goal is to give recommendation for the use of dopamine agonists to the German health system. A systematic literature search was done. The identified studies have different methodological quality and investigate different hypothesis and different outcome criteria. Therefore a qualitative method of information synthesis was chosen. Since the introduction of L-Dopa in the 1960´s it is considered as the most effective substance to reduce all the cardinal symptoms of Parkinson disease. This substance was improved in the course of time. Firstly some additional substances were given (decarbonxylase inhibitors, catechol-o-transferase inhibitors (COMT-inhibitors), monoaminoxydase-inhibitors (MAO-inhibitors) and NMDA-antagonists (N-Methyl-d-aspartat-antagonists). In the practical therapy of Parkinson dopamine agonists play an important role, because they directly use the dopamine receptors. The monotherapy of Parkinson disease is basically possible and is used in early stages of the disease. Clinical practise has shown, that an add on therapy with dopamine agonists can led to a reduction of the dose of L-dopa and a reduction of following dyskinesia. The studies for effectiveness include studies for the initial therapy, monotherapy and add-on-therapy. Basically there is a good effectiveness of dopamine agonists the reduce dyskinesia and this differences are statistically significant. The effect of dopamine agonists is weaker then levodopa generally. The initial therapy with dopamine agonists can postpone the use of levodopa medication or keep the dose small for a longer period of time. There are more other side effects to levodopa, these are not statistically significant. The idea, which strategy for the treatment should be chosen is dependent of several factors and has to be evaluated with the individual patient. An important criterion is the age of the patient at the beginning of the treatment. For younger patients (under 65 years) the risk of developing motoric fluctuation and dyskinesia is much higher and therefore it is proposed to use levodopa at later stages. The evidence of the evaluated studies show a good effectiveness with the therapy of Parkinson disease as monotherapy of younger patients or as additional medication to levodopa as well as older patients with progressive stages of this disease. In these groups of patients there is a positive cost-benefit ratio.