Levodopa (Madopar and Sinemet)

Levodopa has been used to treat the symptoms of Parkinson's since the 1960s. It is a natural amino acid that the brain converts into dopamine and so it replaces the missing chemical.

The commonly prescribed forms of levodopa are:

• Madopar (co-beneldopa)
• Sinemet (co-careldopa)

Both contain an extra substance that prevents levodopa being changed to dopamine before it reaches the brain. Madopar contains levodopa plus benserazide and Sinemet contains levodopa plus carbidopa.

People with Parkinson's are usually started on a low dose and this is gradually increased until they and their GP/consultant feel that there has been a satisfactory response.

There are a number of forms of Madopar and Sinemet containing different amounts of the drugs.

Dispersible Madopar

Madopar has a dispersible form that may be swallowed whole or dissolved in water. Absorption of the dispersible form is quicker and can be used to 'kick start' people with Parkinson's. It can also be used in cases where control of the Parkinson's is difficult with standard levodopa. People who have difficulty swallowing tablets or capsules may also find this beneficial.

Once dispersed, the preparation leaves a chalky residue at the bottom of the glass that does not contain the drug.

Madopar capsules should NOT be broken.

Controlled release (CR) preparations of Madopar and Sinemet

Controlled release preparations are recognised by the letters CR after the drug name. The drug is released over a four- to six-hour period and may result in less fluctuation of levodopa levels in the blood. When changing from standard to controlled release preparations up to 30 percent more levodopa can be needed.

With controlled release preparations the time between doses can sometimes be prolonged by 30-50 percent. They may be used when a person with Parkinson's is experiencing 'wearing-off' of the dose of standard levodopa. They can also be taken before going to bed to reduce stiffness and immobility during the night.

Advantages of levodopa

Most people can tolerate Sinemet or Madopar and experience considerable long-term improvement, especially in stiffness and slowness of movement.

Disadvantages of levodopa

In the early days of taking these tablets some feelings of sickness and nausea are common. However, in most people, they are usually mild and pass as the body adjusts to the drug. 

A small percentage of people cannot tolerate these drugs at all because of severe sickness, or other side effects such as confusion, hallucinations, mood swings or psychological changes.

In the longer term, the response to these drugs can become less reliable, and people may experience increasing periods when the effect of the most recent dose wears off before the next one is due or has begun to work (end-of-dose deterioration). Unwanted involuntary movements (dyskinesias) may appear, and there may be sudden switches from being 'on' and able to move to being 'off' and immobile. 

These longer-term effects can sometimes be improved by altering the type or amount of Sinemet or Madopar, or the frequency with which the drug is taken. If this is not satisfactory, other types of drug can be combined with levodopa.