Can COMT inhibitors improve cognitive functions in patients with Parkinson's disease?

Catechol-O-methyltransferase (COMT) inhibitors are used in patients with Pa rkinson's disease to reduce the complications associated with long term lev odopa therapy. By inhibiting catecholamine catabolism: they extend the phar macological effects of levodopa and improve patient disability. Also as a result of the inhibition of catecholamine catabolism, COMT inhibi tors may have some positive effects on cognitive functions and on some psyc hiatric symptoms, such as depression, that can occur in individuals with Pa rkinson's disease. Animal studies have shown that COMT inhibitors may exert a positive effect on some cognitive functions, such as short term and working memory, and lea rning. However, results of these studies are, in some cases, difficult to i nterpret. One clinical study of patients with Parkinson's disease who were treated with the COMT inhibitor tolcapone as an adjuvant to long term levod opa therapy showed a positive effect on several cognitive aspects. These re sults warrant a wider investigation of the cognitive effects of COMT inhibi tors in patients with Parkinson's disease.