Treatments: COMT Inhibitors

Names:

How They Work:

COMT inhibitors (short for catechol-O-methyltransferase) are a rather newly developed line of defense against Parkinson's Disease. Although similar to MAO-B inhibitors that work by preventing the breakdown of dopamine by MAO-B enzymes, the COMT inhibitor tolcapone prevents the breakdown of both dopamine and L-dopa by COMT enzymes in both the central and peripheral nervous system (Entacapone cannot cross the blood-brain barrier, and only works peripherally). Administration of COMT inhibitors increases the availability of dopamine and L-dopa in the body, increases the concentration of dopamine, and increases the effectiveness of L-dopa treatments (because the introduced L-dopa is not broken down before it reaches the brain). The COMT enzymes that would break down the dopamine in the brain are also disabled by the inhibitor drug, and so dopamine successfully stimulates the necessary neurons to control motor functions that are inactive in patients with Parkinson's. Therefore, a higher percentage of the L-dopa administered to a patient is used by the body, and less of a dose is needed to maintain the same level of treatment. Decreasing the dosage often reduces the diskinesias associated with L-dopa.

In clinical trials of one of these drugs, trade-named Tasmar (generic name tolcapone), patients with a stable response to L-dopa showed significant improvements in daily skills like walking and writing (Henkel 1998). After one year, their improvements remained stable. The side effects may include DID, but this can be avoided by decreasing L-dopa dosage (Gregory 1999).

Side-Effects:



Information from:

Parkinson's Disease at Harvard

http://www.psychweekly.com/aspx/Article/articledetail.aspx?articleid=617

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