Levodopa

How does it work?

Levodopa can be changed into dopamine in the body and in the brain. Therefore, it directly supplies the brain with more dopamine (see Figure, below).

Levodopa is always prescribed with other medications such as dopa-decarboxylase inhibitors (DDIs) and COMT inhibitors, which prevent it from being broken down before it reaches the brain. Combination with these other medications reduces the dose of levodopa needed, and prevents some unpleasant side effects.

What are the benefits?

Levodopa is a well-established treatment for Parkinson’s disease (PD), and is thought of as the ‘gold standard’ treatment. Most people with PD will be prescribed levodopa at some point during their therapy.

Levodopa is very effective at preventing slow movements and stiffness, especially in the early stages of PD. It is also used to reduce tremor.

What are the side effects?

Levodopa may cause side effects including nausea, vomiting, low blood pressure upon standing, sleepiness, hallucinations and abnormal dreams.

Those people who have had PD for a number of years will begin to experience changes in the effectiveness of levodopa – freezing, and ‘wearing off’ and ON–OFF fluctuations. In addition, dyskinesias (restless movements) may begin to appear.

Some of the side effects of levodopa (e.g., vomiting) may disappear over time, while others may be improved by a reduction in dose or use of a slow-release form of levodopa. Medication can be prescribed to help relieve nausea, and this should be discussed with a doctor or PD nurse.

The Duodopa^® pump

As well as oral tablets (Sinemet^®), the combination of levodopa and carbidopa can also be administered in a form known as Duodopa^®. Duodopa^® contains the two medications in a gel that is delivered directly into the digestive tract (duodenum), via a tube from a portable pump operated by the person with PD or a carer. The tube is inserted in a minor surgical operation.

This delivery system is designed to provide a more even supply of the medication, which is not influenced by emptying of the stomach, thereby potentially reducing the occurrence of wearing off, and ON–OFF fluctuations.

How levodopa works

(Click on animation to enlarge.)