Environmental Photochemistry of Altrenogest: Photoisomerization to a Bioactive Product with Increased Environmental Persistence via Reversible Photohydration.

Despite its wide use as a veterinary pharmaceutical, environmental fate data is lacking for altrenogest, a potent synthetic progestin. Here, it is reported that direct photolysis of altrenogest under environmentally relevant conditions was extremely efficient and rapid (half-life ∼25 s). Photolysis rates (observed rate constant kobs = 2.