Pharmaceuticals are ubiquitous contaminants in aquatic ecosystems. Adaptive monitoring, assessment and management programs will be required to reduce the environmental hazards of pharmaceuticals of concern. Potentially underappreciated factors that drive the environmental dose of pharmaceuticals include regulatory approvals, marketing campaigns, pharmaceutical subsidies and re-imbursement schemes and societal acceptance. Sales data for five common antidepressants (Cymbalta, Lexapro, Effexor, Wellbutrin, Zoloft) in the United States of America from 2004 to 2008 were modelled to explore how environmental hazards in aquatic ecosystems changed after patents were obtained or expired. Therapeutic hazard ratios (THR) for Effexor and Lexapro did not exceed 1; however, the THRs for Zoloft declined whereas the THR for Cymbalta increased as a function of patent protection and sale patterns. These changes in THR highlight the importance of considering current and future drivers of pharmaceutical use when prioritizing pharmaceuticals for water quality monitoring programs. When examining urban systems receiving discharges of environmental contaminants, water quality efforts should identify, prioritize and select target analytes presently in commerce for effluent monitoring and surveillance.