Climate Change and Medications: Implications for Clinical Practice, Healthcare Sustainability, and Pharmacoepidemiology

Key Points The climate‐medication relationship is bidirectional: climate‐amplified exposures such as extreme heat affect medication access, stability, and safety/effectiveness (downstream), while the use and disposal of medications add to healthcare's carbon footprint, thereby contributing to the very warming that intensifies those exposures (upstream). Downstream: Extreme heat, extreme weather, and supply chain disruption are concrete threats to drug stability and access, from mail‐order degradation of insulin and epinephrine to the Hurricane Helene IV‐fluid shortage, and environmental exposures may alter the effects of common medications. Upstream: Therapeutically equivalent options can differ substantially in carbon intensity; eliminating unnecessary prescribing and selecting lower‐carbon therapeutic equivalents are the levers most directly available to prescribers and pharmacists. The evidence base is still immature: current drug‐heat warnings rest largely on mechanistic evidence and case reports, and advancing the field requires linking environmental exposure data to medication outcomes through case‐crossover and time‐series designs, where confounding by indication and polypharmacy represent central challenges. Where lower‐carbon options are already guideline‐concordant, clinicians and pharmacists can act now through prescribing choices, patient education on heat precautions and proper medication storage and disposal, along with healthcare system preparedness. Broader change requires guideline revision, formulary reform, transparent industy data, and collective action through professional societies, including the International Society for Pharmacoepidemiology.