Early use of COMT inhibitors and/or use of MAO-B inhibitors may potentially reduce the motor fluctuations that are common in PD [16] Unfortunately, genetic testing of patients with PD is not easily accessible, and though it may have a valuable contribution to personalizing treatment, pharmacogenetic testing (also called pharmacogenomic testing)—which typically includes COMT genotyping—is not offered to patients [17]. Here, COMT is linked to Parkinson disease.