Which COMT inhibitor does not significantly affect liver function?

Entacapone is a selective catechol-O-methyltransferase (COMT) inhibitor used primarily in the treatment of Parkinson's disease to enhance the effects of levodopa by preventing its degradation. One of the key characteristics that distinguishes entacapone from other COMT inhibitors, particularly tolcapone, is its safety profile concerning liver function.

Tolcapone, while effective in managing symptoms of Parkinson's disease, can lead to hepatotoxicity and requires regular monitoring of liver enzymes during treatment. In contrast, entacapone is not associated with significant impairment of liver function, making it a safer choice from this perspective for long-term management in patients.

Selegiline and amantadine, although relevant to Parkinson's disease treatment, do not function primarily as COMT inhibitors and are therefore not directly comparable in this context. Selegiline is a monoamine oxidase B inhibitor, and amantadine primarily enhances dopaminergic activity. Thus, the combination of efficacy without major liver toxicity positions entacapone as the appropriate choice in this question.