Chemistry:Difethialone
Difethialone is an vitamin K antagonist anticoagulant used as a rodenticide.[1] It is considered a second generation agent.[2]
It belongs to the 4-thiochromenone or benzothiopyranone class of rodenticides, which differs from 4-hydroxycoumarins by the substitution of an oxygen atom with sulfur. It is especially similar to brodifacoum. It shares the same mechanism of inhibiting Vkorc1. It is effective for warfarin-resistant and warfarin-susceptible rodents.[1] Its high potency makes resistance harder to evolve, though a few populations of rodents have nevertheless managed to do so.[3]
In May 2008, the Environmental Protection Agency (EPA) added restrictions on the sale of difethialone in consumer-use rodenticide products and also for exterior use by commercial applicators.[4][5]
Regulations
The EPA began analyzing anticoagulant-based rodenticide products (AR) in the 1990s.[6] The results were published in 1998 "in the Registration Eligibility Decision (RED) rodenticide cluster (US EPA 1998)."[6] Difethialone was classified as suitable for registration. A further in-depth environmental risk assessment using the "stochastic risk assessed method" targeted the nine active ingredients in rodenticides.[6] Products containing difethialone were identified as hazardous to non-target animals. In 2008, to protect children and prevent animal exposure, the EPA published its final decision. California further restricted the use of difethialone. "Assembly Bill No. 2657 prohibits the use of brodifacoum, bromadiolone, difenacoum, and difethialone in 'wildlife habitat areas,'" and "Assembly Bill 2596" prohibits their use in the state, with an exemption for agricultural use.[6]
In the EU, rodenticides are regulated as pesticides when used to protect growing or stored crops, and as biocides when used to protect processed agricultural produce stored in farm buildings.[6] The EU, however, still allows the use of ARs; however, manufacturers of difethialone have not sought authorization for crop protection.[6]
In Australia, difethialone is classified as a Schedule 6 anticoagulant rodenticide. "Schedule 6. – Poison – Substances with a moderate potential for causing harm, the extent of which can be reduced through the use of distinctive packaging with strong warnings and safety directions on the label."[7][6] The sale and use of difethialone is legal according to the Australian Government Department of Health, Therapeutic Goods Administration, 2017.[7]
References
- ↑ 1.0 1.1 "Difethialone (LM-2219): a new anticoagulant rodenticide for use against warfarin-resistant and -susceptible strains of Rattus norvegicus and Mus musculus". Annales de Recherches Vétérinaires 20 (2): 159–64. 1989. PMID 2751229. https://hal.archives-ouvertes.fr/hal-00901856.
- ↑ "Field evaluation of difethialone, a new second generation anticoagulant rodenticide in the rice fields". Indian Journal of Experimental Biology 41 (6): 655–8. June 2003. PMID 15266918.
- ↑ McGee, C.F.; McGilloway, D.A.; Buckle, A.P. (September 2020). "Anticoagulant rodenticides and resistance development in rodent pest species – A comprehensive review". Journal of Stored Products Research 88. doi:10.1016/j.jspr.2020.101688.
- ↑ "Restrictions on Rodenticide Products" (in en). 2014-03-04. https://www.epa.gov/rodenticides/restrictions-rodenticide-products.
- ↑ "Regulations.gov". https://www.regulations.gov/document?D=EPA-HQ-OPP-2006-0955-0764.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 Eisemann, John D.; Fisher, Penny M.; Buckle, Alan; Humphrys, Simon (2018), van den Brink, Nico W.; Elliott, John E.; Shore, Richard F. et al., eds., "An International Perspective on the Regulation of Rodenticides" (in en), Anticoagulant Rodenticides and Wildlife (Cham: Springer International Publishing): pp. 287–318, doi:10.1007/978-3-319-64377-9_11, ISBN 978-3-319-64377-9, https://doi.org/10.1007/978-3-319-64377-9_11, retrieved 2025-12-13
- ↑ 7.0 7.1 Lohr, Michael T.; Davis, Robert A. (2018-09-01). "Anticoagulant rodenticide use, non-target impacts and regulation: A case study from Australia". Science of the Total Environment 634: 1372–1384. doi:10.1016/j.scitotenv.2018.04.069. ISSN 0048-9697. https://www.sciencedirect.com/science/article/pii/S0048969718312336.
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