Measurements in the environment and effect data on aquatic organisms are missing, even internationally. Ulipristal is not considered to be readily degradable (theoretical assessment). One of the urine metabolites of ulipristal is active. Estimated fat solubility (log Pow) for ulipristal is high enough to cause significant bioconcentration in fish. Note that calculation of ulipristal acetate's ability to bioaccumulate is irrelevant, as ulipristal acetate is the more water-soluble prodrug that will not reach the environment.
Ulipristal does not bind to the Sex Hormone Binding Globulin (SHBG) as opposed to levonogestrel. Binding to SHBG is suspected to be an important cause of the exceptionally high bioconcentration ability (and thus potency) observed in fish for levonorgestrel. Therefore it is possible that ulipristal accumulates less in fish compared to levonorgestrel despite higher log Pow.
The replacement of levonorgestrel with ulipristal as an emergency contraception pharmaceutical may only cause small effects of the levonogrestrel concentration in the environment, as the replacement includes only part of the use of levonorgestrel. At the same time, exchange may result in a corresponding increase in the level of ulipristal in the environment.
It is unclear whether ulipristal is less potent for fish than levonorgestrel is. If ulipristal accumulates in fish to levels approaching therapeutic levels, it is likely that the reproduction may be disturbed, based on the effect mechanism. Due to insufficient data about both levels in the environment and effects of ulipristal, risk assessments are very uncertain. Therefore, from an environmental point of view, a levonorgestrel replacement of ulipristal is not recommended, but it may be relevant if relevant data on environmental spreading, bioconcentration and effects are obtained for ulipristal.
Author: The Pharmaceutical unit of Region Stockholm