Levodopa

Levodopa (L-dopa) is the most commonly used medicine for Parkinson's disease. It is given orally or as a gel directly into the gastro-intestinal tract. L-dopa is then carried to the duodenum by a tube connected to a portable pump which is operated by the patient. The tube is inserted surgically. This method of administration allows a more even distribution of the medicine.

How does L-dopa act?

L-dopa is a precursor of dopamine. It is rapidly converted into dopamine due to the action of dopa decarboxylase (DDC), an enzyme present in the gastro-intestinal tract and in the liver. It then passes from the blood to the brain. Addition of this synthetic dopamine compensates for deficiency of natural dopamine.

Do they have contraindications or precautions?

The side effects of L-dopa include involuntary movements (dystonia) and tremor. Drowsiness, gastro-intestinal problems (nausea, vomiting) and cardiovascular problems (orthostatic hypotension, dysrhythmias) can also occur. Patients can also develop psychological problems (acute confusion, hallucinations), behavioural disturbances or depressive features.

Sources:

• Merck Manuel, 4^th edition
• Interview with Jean-Philippe Brandel, neurologist at the Léopold Bellan Hospital, Paris, on www.infopatients-lundbeck.fr, 7 July 2011
• MyPDinfo.com, 7 July 2011