Methadone
Summary
Persistence. Methadone is potentially persistent.
Bioaccumulation. Methadone has low potential for bioaccumulation.
Toxicity. Methadone has moderate chronic toxicity.
Risk. The use of methadone (sales data Sweden 2023) has been considered to result in insignificant environmental risk.
This summary information comes from fass.se.
Detailed information
Comment on Fass environmental information
Methadone has different classifications on fass.se. According to Lif (the trade association for the research-based pharmaceutical industry in Sweden) the various pharmaceutical companies compile environmental information for their active substances based on internal studies and published data. Based on data, which may thus differ between different pharmaceutical companies, the companies assess the environmental risk with guidance from “Environmental classification of pharmaceuticals at www.fass.se – Guidance for pharmaceutical companies 2025 v 1.0”. The Swedish Environmental Institute (IVL) reviews the assessment but does not have the task of coordinating/harmonizing environmental information from different pharmaceutical companies for the same active substance.
Fass environmental information Metadon Nordic Drugs
Fass environmental information for Metadon Nordic Drugs from Nordic Drugs AB (retrieved on 2025-11-11).
Hazard
Persistence: "Methadone hydrochloride did not pass the ready biodegradation test (OECD Guideline 301 A) and there is no data on mineralization. The phrase “Methadone hydrochloride is potentially persistent” is thus chosen."
Bioaccumulation: Log Kow = 2.07 at pH 7.4.
Toxicity: There are data for 3 trophic levels, most sensitive crustacean NOEC 190 microg/L.
Risk
PEC/PNEC is based on sales data in Sweden in year 2023.
PEC = 0.0123 microg/L.
PNEC = Lowest NOEC, 190 microg/L/50 (Assessment Factor (AF) for 2 chronic studies) = 3,8 microg/L.
PEC/PNEC = 0.00347 which gives the risk insignificant.
Fass environmental information Metadon Viatris
Fass environmental information for Metadon Viatris from Viatris AB (retrieved on 2025-11-11).
Hazard
Persistence: No data.
Bioaccumulation: Log Pow = 3.93 (unknown method).
Toxicity: No data.
Risk
PEC/PNEC is based on sales data in Sweden in year 2022.
PEC = 0.013 microg/L.
Environmental risk of methadone cannot be excluded due to lack of ecotoxicological data.
Fass environmental information Metadon Abcur
Fass environmental information for Metadon Abcur from Abcur AB (retrieved on 2025-11-11).
Hazard
Persistence: No data.
Bioaccumulation: Log Pow = 3.93 (unknown method).
Toxicity: No data.
Risk
PEC/PNEC is based on sales data in Sweden in year 2021.
PEC = 0.0138 microg/L.
Environmental risk of methadone cannot be excluded due to lack of ecotoxicological data.
References
Author: Health and Medical Care Administration, Region Stockholm