Green Pharmacology and Ecotoxicity of Pharmaceuticals: A Comprehensive Review of Environmental Impact and Gaps in Ecologically Conscious Drug Design

Pharmaceuticals are indispensable pillars of modern medicine; however, their pervasive release into the natural environment through multiple pathways—including patient excretion, inadequate wastewater treatment, agricultural runoff, and improper disposal—has emerged as a formidable global ecological concern. This comprehensive review critically examines the environmental impact of pharmaceuticals across terrestrial, aquatic, and atmospheric compartments and evaluates the conceptual and practical foundations of Green Pharmacology as an interdisciplinary strategy to mitigate these harms. We analyse the fate, persistence, and ecotoxicological consequences of major pharmaceutical classes—including antibiotics, endocrine-disrupting compounds, non- steroidal anti-inflammatory drugs (NSAIDs), antidepressants, antineoplastic agents, and veterinary pharmaceuticals—drawing on peer-reviewed literature, regulatory documents, and global monitoring data published predominantly within the last two decades. Particular attention is directed toward the "design gap" in pharmaceutical development: the systematic failure to incorporate ecotoxicity endpoints into early-stage drug discovery and approval frameworks. We discuss emerging strategies for ecologically conscious drug design, including the integration of green chemistry principles, ADMET-guided molecular optimisation, in silico ecotoxicity prediction tools, and biologically benign structural analogues. The review further identifies critical research lacunae: the absence of uniform international environmental risk assessment (ERA). requirements, insufficient biodegradability testing, a paucity of ecotoxicity data for metabolites and transformation products, and the underrepresentation of developing nations in pharmaceutical environmental monitoring. Policy recommendations—spanning regulatory reform, incentive structures for green drug synthesis, and circular pharmaceutical stewardship—are proposed. This review underscores an urgent need for paradigm-level integration of environmental sustainability into the pharmaceutical lifecycle, from molecular conception to post-market surveillance.