Plasma superwarfarin levels and vitamin K1 treatment in dogs with anticoagulant rodenticide poisoning.

The plasma concentration, plasma half-life (t1/2), and mean residence time (MRT) of rodenticide anticoagulants were determined in 21 dogs in which a preliminary diagnosis of anticoagulant rodenticide poisoning had been made. Brodifacoum, difethialone, and difenacoum were detected by high-performance liquid chromatography (HPLC) in the plasma of 13, 3, and 2 dogs, respectively. At presentation the plasma concentration ranged from below the detection limit (10 ng/L) to 851 ng/L. Toxin could not be detected in 3 dogs, despite these animals showing characteristic coagulation disturbances and a positive response to therapy with vitamin K1. In 7 dogs the estimated t1/2 of brodifacoum ranged from 0.9 to 4.7 (median 2.4) days with a MRT of 1.9 to 3.7 (median 2.8) days. In 2 dogs the individual t1/2 of difethialone was 2.2 and 3.2 days and the MRT was 2.3 and 2.8 days, respectively. Two dogs died during emergency treatment. Treatment in the remaining 19 dogs consisted of the administration of vitamin K1 and supportive therapy. The dose of vitamin K1 was reduced in a stepwise manner as long as the prothrombin time remained within physiological limits. The variation in initial plasma concentrations of the anticoagulants combined with the results of treatment support the idea that an individual therapeutic approach is warranted.