Developing an Ecotoxicological Classification for Frequently Used Drugs in Primary Care

Most drugs excreted in urine are not filtered by wastewater treatment plants and end up in aquatic systems. At concentrations measured in waters, toxic effects on species have been described. Second, most of the drug consumption is attributable to primary care prescriptions. We thus present here, an ecotoxicity classification of the most sold drugs in primary care in Switzerland. Three datasets were combined: (1) surveyed ecotoxic drugs by the Swiss National Surface Water Quality Monitoring Programme and its European equivalent, (2) the top 50 drugs by sale in primary care in Switzerland, and (3) active pharmaceutical ingredient (API) concentrations in Lake Geneva and the rivers of the canton of Vaud between 2017 and 2022. We classified APIs into five categories from the safest to the least safe: (1) APIs found in concentrations (C) <10× their environmental quality standard (EQS·10^-1), (2) EQS·10^-1 < C < EQS and not listed by the Swiss or the EU Watch List, (3) EQS·10^-1 < C < EQS and listed, (4) C > EQS and not listed, and (5) C > EQS and listed. We obtained full ecotoxicological data for 35 APIs. Fifteen APIs were designated as safe (category (1):paracetamol, tramadol, amisulpride, citalopram, mirtazapine, metformin, gabapentin, lamotrigine, primidone, candesartan, irbesartan, atenolol, hydrochlorothiazide, ofloxacin, sulfadiazine), eleven as intermediately safe, and nine were of concern (azithromycin, ciprofloxacin, clarithromycin, sulfamethoxazole, carbamazepine, diclofenac, ibuprofen, iomeprol, iopromide). Full data were available for only one-third of the drugs most sold in primary care. Where data do exist, we observed significant differences in environmental impact among the same class of drugs. Our classification could therefore help guide doctors to adopt more eco-friendly prescriptions.