Catechol-o-methyltransferase (COMT) inhibitors

 Catechol-o-methyltransferase (COMT) inhibitors are adjunct therapy that helps when levodopa starts to wear off at the end of each dosing interval.

Given typically with each dose of levodopa to increase the amount of “on” time by 1-2 hours each day.

COMT inhibitors work by blocking an enzyme that metabolized dopamine; boosting the effects of levodopa and dopamine by allowing dopamine to remain present longer.

Side effects include worsening of dyskinesia, nausea, diarrhea, and abdominal pain; postural hypotension – drop in blood pressure on sitting or standing up – can also occur.

Entacapaone (Comtan) can also cause urine discoloration.