This policy brief examines post-drug syndromes (PDS) as a structurally neglected category of adverse drug reactions within contemporary pharmacovigilance and public health systems. PDS refer to persistent, multisystem conditions triggered by prescription medications and continuing long after drug discontinuation, with documented examples including Post-Finasteride Syndrome (PFS), Post-SSRI Sexual Dysfunction (PSSD), and related post-retinoid syndromes. Despite increasing patient-reported evidence and selective regulatory acknowledgements, existing pharmacovigilance frameworks remain predominantly optimized for detecting acute, temporally proximate adverse events. As a result, long-term drug-induced harms are systematically under-recognized, misclassified, or excluded from formal safety evaluation, leading to distorted risk–benefit assessments, inadequate informed consent, and prolonged patient morbidity. This brief synthesizes current regulatory signals, patient-reported data trends, and pharmacovigilance literature to identify three core systemic failures: (1) conceptual assumptions of reversibility embedded in safety science, (2) methodological limitations of passive adverse event reporting systems for long-term outcomes, and (3) governance and educational gaps that perpetuate diagnostic and surveillance inertia. The public health implications are substantial, encompassing preventable disability, productivity loss, mental health burden, and erosion of institutional trust. Building on this analysis, the document proposes actionable, system-level recommendations aimed at strengthening long-term drug safety oversight. These include formal recognition of post-drug syndromes within pharmacovigilance frameworks, development of longitudinal reporting mechanisms incorporating patient-reported outcomes, integration of persistent adverse effects into medical education and informed consent practices, and prioritization of mechanistic and epidemiological research to clarify persistence pathways. This work is intended for regulators, public health professionals, pharmacovigilance authorities, and researchers engaged in drug safety, ethics, and population health. It contributes to ongoing discussions on how pharmacovigilance systems can evolve from reactive detection of acute harms toward proactive, life-course–oriented safety surveillance capable of identifying and preventing enduring iatrogenic injury. Version 2 includes minor corrections to author affiliation and formatting, and clarifies reporting limitations. No substantive changes to conclusions. Suggested citation: Nair, V. S. (2025). Post-Drug Syndromes: A Neglected Challenge in Pharmacovigilance and Public Health. Zenodo. https://doi.org/10.5281/zenodo.17999880