What are the side effects of COMT inhibitors?

What are the side effects of COMT inhibitors?

Neal Hermanowicz (Director of the Movement Disorders Program) gives expert video advice on: What are the side effects of Dopamine Receptor Agonists?; What is 'impulse control disorder'? and more...

COMT medications may cause side effects by their mechanism of enhancing the effect of Levodopa. By themselves, they're usually pretty well tolerated. They don't cause much in the way of side effects. COMT inhibitors may cause discoloration of urine, making it an orange or amber color, which is of no significance, but if you don't caution people about it, it could be alarming to them if their urine color has changed. Rarely, not often, they cause diarrhea. In about five or ten percent of people who use these medications, they may get diarrhea. One of the COMT inhibitors, specifically tolcapone, has been associated with some nasty liver effects, in a very small number of people. But it did cause liver injury, and in fact, death, in a few patients after it had been more widely used. For that reason, tolcapone is required to have liver function testing accomplished on a monthly basis for six months, and thereafter according to the judgement of the clinician. Also, baseline liver function tests - these are blood tests - prior to starting the medication. In the United States, it's also requested by the FDA that people sign a form acknowledging they're aware of these potential complications of tolcapone, before initiating the medication.