Which drugs are used to treat Parkinson's disease?
Three types of drugs are commonly used to ease the symptoms of PD - levodopa, dopamine agonists and monoamine oxidase-B (MAO-B) inhibitors. When a drug is first prescribed for PD it is usually one of these three. Other drugs are also sometimes used, usually in addition to one of these three main types of drug.
Levodopa
This drug has been used for many years. Nearly all people with PD notice a good improvement in symptoms after starting levodopa. The body converts levodopa to dopamine. Therefore, the low level of dopamine in the affected part of the brain increases with levodopa. A low dose is usually started at first. Over time, the dose often needs to be increased to control the symptoms.
Levodopa is always combined with another drug (either benserazide or carbidopa). These prevent levodopa from being converted into dopamine in the bloodstream. This reduces side-effects and increases the amount that gets to the brain where it is converted to dopamine. The combination of levodopa and benserazide is called co-beneldopa, and the combination of levodopa and carbidopa is called co-careldopa. (The common brand names for these are Sinemet and Madopar.)
Side-effects sometimes occur when you first start levodopa, although most people have no problems with low doses. Read the leaflet in the drug packet for a full list of possible side-effects. Nausea (feeling sick) is the most common, but less likely to occur if you take a small dose at first, and then gradually build it up. If nausea is a problem, then it can usually be eased by an anti-sickness drug called domperidone.
Levodopa tends to work less well over time, and the dose usually needs to be increased every now and then. Unfortunately, over time as the dose increases (typically after several years), most people taking levodopa develop problems. These include 'on-off' effects. This is where you can switch quite suddenly between being 'on' and able to move, and being 'off' and immobile. Muscle problems also commonly develop which can cause uncontrollable jerky movements and other effects (dyskinesias). These problems related to long-term use of levodopa can become quite disabling, tiring and painful.
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