It is less toxic than l-dopa, but also less effective. It is usually used early in the progression of the disease and loses efficacy in 6-8 months. This drug is used early in treatment as an alternative to l-dopa or as an adjunct later in therapy. This is a relatively new approach to augmenting l-dopa therapy. By inhibiting the enzyme, blood concentrations of l-dopa are higher, and more can enter the brain.
Studies show a significant improvement in response.
The principle of this use is based on the fact that there are cholinergic fibers in the striatum which have opposite effects to those of the dopaminergic neurons. Antagonizing acetylcholine therefore serves to balance the diminished dopaminergic activity seen in Parkinsonism. Anticholinergic drugs are effective, but basically inferior to l-dopa. They therefore are used as adjuncts or as the sole therapy early in the disorder. These drugs are also the primary drugs used to treat drug-induced Parkinsonism.