Among the initial PEs for patients with a first-listed diagnosis of PD, the most frequent prescribed antiparkinsonian medication is Levodopa (n = 1,450), followed by Dopaminergic agonist (n = 831), MAO-B inhibitors (n = 145), COMT inhibitors (n = 120), Amantadine (n = 32), and Anticholinergics (n = 30). This evidence concerns the gene COMT and Parkinson disease.