Mifepristone
Summary
Persistence. Mifepristone is degraded in the environment.
Bioaccumulation. Mifepristone has low potential for bioaccumulation.
Toxicity. Mifepristone has very high chronic toxicity.
Risk. Since concentrations downstream of wastewater treatment plants are likely below 0.1 ng/L in most cases (Golovko et al., 2018; Liu et al., 2010), the environmental risk in Sweden is considered relatively low, even though mifepristone is likely potent in fish. No effect data on fish exist for the desmethyl metabolites of mifepristone, but they are presumably less potent than mifepristone itself.
This summary information comes from Fass. The environmental risk originates from the Goodpoint 2024 report.
Detailed information
Fass environmental information
Fass environmental information for Mifegyne (mifepristone) from Nordic Drugs (downloaded 2025-05-13).
Hazard
Persistence: The DT50/DT90 values for mifepristone are 4.5/14.9 days (water phase), 72.1/239.0 days (sediment phase) and 14.3/212.0 days (total system) for sediment system A and 4.1/13.5 days (water phase), 29.6/98.4 days (sediment phase) and 12.7/42.3 days (total system) for sediment system B. DT50 values obtained for the total system for both test systems (A and B) are therefore ≤ 14.3 days, and the substance is degraded in the environment (DT50 ≤ 32 d).
Bioaccumulation: Experimental Log Kow is 4.61, however the estimated bioconcentration factors derived from the mifepristone bioaccumulation study in fish as per OECD 305 were below 25 L/kg. Mifepristone bioaccumulation potential can therefore be considered to be low (BCF < 500) and the phrase “Mifepristone has low potential for bioaccumulation” is thus chosen.
Chronic toxicity: There are data for 3 trophic levels, most sensitive fish (Danio rerio) NOEC 0.1 microg/L.
Risk
PEC/PNEC is based on sales data in Sweden in year 2020. PEC/PNEC = 0.05686 which gives the risk insignificant.
Report Goodpoint 2024
The report from Goodpoint 2024 aims to present an overall, comparative assessment of the treatment options recommended for all indications within the gynecology and obstetrics therapeutic area in the 2024 edition of the Wise list (the formulary for Region Stockholm, Sweden) containing either estrogens or progestogens + estetrol. The risk assessment does not aim to evaluate absolute or quantitative risk (which, for example, strongly depends on dilution in different recipients) but is primarily of a comparative nature, i.e., a ranking of the risk between different treatment options. See the report for further details.
Author: Health and Medical Care Administration, Region Stockholm