Parkinson's disease cannot be completely cured yet. Still, people have tried to cure it with drugs. One treatment is to put back the lost dopamine. A group of drugs called dopamine receptor agonists acts similarly to dopamine when put in the brain. There are four different drugs included in that group. Many patients take one of those with another drug. That other drug is called L-dopa. Unlike the dopamine, the L-dopa can enter the brain. The dopamine cannot enter the brain. This is why many patients take L-dopa and dopamine together. In the beginning, L-dopa helps a lot. But as the disease develops, the L-dopa doesn't work as well. Two other drugs used are anticholinergics and selegiline. They both help lessen symptoms. Anticholinergics help the patient stop shaking. Selegiline is meant to protect the nerves in the central nervous system. Selegiline is not often used. This is because there is no real proof that it helps.