How does levodopa help Parkinson's disease?

Levodopa is a medication that is used to treat people with Parkinson’s disease and those with Parkinson’s-like symptoms that have developed due to an injury or illness. It was discovered in the 1960s.

Parkinson’s disease is a progressive, neurodegenerative disorder. The symptoms of Parkinson’s are caused by a lack of dopamine in an area of the brain called the corpus striatum and commonly include a tremor or shaking while at rest, stiffness and slowness of movement (bradykinesia).

Dopamine is a neurotransmitter, or messenger, that passes signals between nerve cells and is involved in regulating the signals involved in movement.

What does levodopa do for Parkinson’s disease?

Levodopa is a central nervous system agent that helps people with Parkinson’s because it is converted into dopamine in the brain. It helps to alleviate the symptoms of Parkinson’s disease by providing a supply of dopamine.

Simply treating people with Parkinson’s disease with dopamine does not work because dopamine can not cross the blood-brain barrier. Levodopa - a metabolic precursor of dopamine - can cross the blood-brain barrier, however.

Levodopa is available in a range of different dosage forms that combine levodopa and carbidopa, such as Sinemet tablets.

Carbidopa is a decarboxylase inhibitor that prevents levodopa from being broken down before it reaches its site of action, the brain. It enables lower doses of levodopa to be used, which reduces the nausea and vomiting patients can experience while taking the drug.

Which Parkinson’s disease symptoms does levodopa help treat?

Levodopa works best to help treat the slowness and stiffness or rigidity associated with Parkinson’s disease, and in some cases may treat the tremor as well.

Does levodopa slow the progression of Parkinson’s disease?

Levodopa does not slow or reduce the progression of Parkinson’s disease. In a clinical trial, levodopa + carbidopa was found to have no disease-modifying effect when it was used in patients with early Parkinson’s disease compared with patients who started it later on in the course of their disease.