Parkinson's disease — rotigotine
Parkinson's disease is a distressing degenerative disorder characterised by tremor and rigidity. It is the result of a deficiency of dopamine within the brain, caused by the degeneration of the substantia nigra.
The treatment of Parkinson's disease was revolutionised by the discovery that administering the dopamine prodrug levodopa, which restored dopamine levels in the brain, gave symptomatic relief. The alternative is treatment with anticholinergic drugs, which restore the balance between dopamine and acetylcholine in the brain.
Dopamine D2 agonists remain the most common method of treatment, and various such compounds are in development. A new D2 agonist, rotigotine, previously referred to as N-0923, is being developed by Schwarz Pharma as a potential treatment for Parkinson's disease. Where it differs from standard D2 agonist treatment is that it is being investigated as a transdermal patch system. Rotigotine has antiparkinson effects when administered intravenously. However, an adhesive matrix patch has been developed to deliver the drug transdermally.
Placebo or doses of 4.5, 9, 13.5 or 18mg of rotigotine were given daily to 242 patients over a 16-week trial period.1 Patients given the higher doses showed significant improvements in their symptoms. Adverse skin reactions were more common with higher doses.
In a Phase II trial to investigate the effectiveness of the patches at replacing levodopa, 85 patients were given placebo or one of four doses of rotigotine using the patch system for 21 days, alongside levodopa.2 Greater reductions in the amount of levodopa administered were seen at the two highest dose patches: 33.5mg rotigotine reduced levodopa use by 26%, and 67mg rotigotine by 28%. Rotigotine was both safe and well tolerated.
The potential advantage of the patch system over oral therapy is that the development of motor problems in Parkinson's patients has been linked with intermittent stimulation of the dopamine receptors, so providing a continuous supply of D2 agonist could prevent this. Rotigotine patches are currently undergoing Phase III trials, and could prove an important addition to the available drug therapies for Parkinson's disease.