Several drug classes have been explored for treating PD, leveraging their potential neuroprotective, symptomatic, or disease-modifying effects. Some of these drugs are well identified in treating other diseases. Drug repurposing offers a promising strategy for identifying new treatments for PD by leveraging existing drugs with known safety profiles and mechanisms of action. The occurrence of certain drug class concepts within the PD research area in the documents of the CAS Content Collection are illustrated in Figure .