- If the subject is receiving an anticholinergic agent (eg, benztropine, trihexyphenidyl, parsitan, procyclidine, biperiden), a monoamine oxidase B (MAO-B) inhibitor (eg, selegiline), a COMT inhibitor (eg, entacapone), or an N-methyl-d-aspartate (NMDA)-antagonist (eg, amantadine), he/she must have been on a stable dose for at least 28 days prior to the Baseline Visit and must be maintained on that dose for the Treatment Period