Anticoagulant-resistant rats: possible control by the use of the chloro analog of vitamin K 1 .

Strains of wild rats that are resistant to the anticoagulant action of coumarins and derivatives of indandione have been discovered in a number of geographic areas. These rats have now been shown to be more susceptible than normal rats are to the anticoagulant action of the vitamin K antagonist, 2-chloro-3-phytyl-1,4-naphthoquinone. This compound, either alone or in combination with warfarin, would appear to be an effective rodenticide in areas where resistance to the indirect anticoagulants is a problem.