This is the start of a new series of articles on Parkinson's drugs.

In the first episode we start with a simple overview of the drugs and how they work, and in the next few chapters we will go into more detail about the individual drug groups and types.

Many say or think: My previous medicines no longer work - they have been used up - the body has become too used to them. This assessment is almost always wrong. The effect of the medication does not wear off. But Parkinson's is getting worse. And he needs a higher dose, a more precise regimen or additional medication.