Drug-Induced Parkinsonism: A Structured, Mechanism-Informed Approach to Identification and Management

Drug-induced parkinsonism (DIP) is an underrecognized form of secondary parkinsonism that can mimic idiopathic Parkinson's disease yet is largely reversible. While the use of first-generation antipsychotics has declined, additional agents, including valproate, cyclosporine, vesicular monoamine transporter 2 inhibitors, and Rauwolfia serpentina-based herbal supplements, have emerged as notable contributors. This narrative review synthesizes epidemiologic, mechanistic, and clinical data from 2009 to 2025 to provide a structured, mechanism-informed approach for clinicians. Across studies, DIP accounted for roughly 15-20% of secondary parkinsonism, disproportionately affecting older adults and women. Functional imaging with dopamine transporter single-photon emission computed tomography typically demonstrates preserved striatal uptake, aiding differentiation from neurodegenerative parkinsonism. Recovery usually occurs within six to 12 months of discontinuing the offending agent, though a minority may experience persistent symptoms. The proposed three-step approach emphasizes comprehensive medication and supplement review, recognition of characteristic clinical patterns, and timely withdrawal with follow-up to confirm reversibility. This framework supports safer prescribing practices, reinforces clinician education, and enhances detection of this preventable condition.