Used only in conjunction with carbidopa/levodopa therapy, COMTAN is a COMT (catechol-O-methyl-transferase_ inhibitor indicated for patients with idiopathic Parkinson's disease experiencing the signs and symptoms of end-of-dose wearing-off. COMTAN is available as tablets containing 200-mg entacapone. The most common side effects of COMTAN therapy are dopaminergic in nature )eg, dyskinesias, nausea). Other common side effects include diarrhea, hyperkinesias, urine discoloration, fatigue, pain, and hallucinations. In rare cases, COMTAN therapy may be associated with orthostatic hypotension, rhabdomyolysis, severe diarrhea, and symptoms resembling neuroleptic malignant syndrome. To manager dopaminergic side effects, reductions in the levodopa dose or dosing frequency may be necessary. However, rapid withdrawal or abrupt reduction of carbidopa/levodopa therapy and COMTAN therapy should be avoided. COMTAN therapy should not be used with nonselective monoamine oxidase (MAO) inhibitors, with selegiline at doses higher than 10mg per day, or with STALEVO (carbidopa/levodopa). Drugs metabolized by the COMT enzymes (eg, isoproterenol, epinephrine) should be used with caution in patients receiving COMTAN therapy. COMTAN should be used with caution in patients with hepatic impairment.