vitamin-k-semiquinone-radical and difethialone

Vitamin K antagonist rodenticide pharmacodynamics (PD) is studied in rodents with traditional laboratory tests. We wondered if thrombin generation test (TGT) could add value. Difethialone (10 mg/kg) was administered per os to 97 OFA-Sprague Dawley rats. PD was studied over a 72 h-period using the Calibrated Automated Thrombogram on platelet poor plasma before and after intoxication (3 female and 3 male rats for each 13 time points) and TGT parameters were compared with the prothrombin time (PT) and vitamin K dependent factor activities previously reported. Following intoxication, preliminary tests evidenced rapid and full inhibition of thrombin generation triggered with 5 or 20 pM human recombinant tissue factor. To study the evolution of TGT parameters following difethialone intake, we adapted the test by complementing intoxicated rat samples with pooled normal rat plasma (3/1, v/v). Adapted TGT confirmed the known higher procoagulant basal level in females compared to males through higher endogenous thrombin potential (ETP) and peak height (PH) (p < 0.0001 and p = 0.0003, respectively). An exponential model fitted well the PH and ETP decay after intoxication. In contrast to PT, the decreases were observed immediately following VKA intake and had comparable time to halving values: 10.5 h (95% CI [8.2; 13.6]) for ETP and 10.4 h (95% CI [7.8; 14.1]) for PH. The decrease of FVII and FX preceded that of PH, ETP and FII while FIX decreased later on, contributing to the severe hypo-coagulability. We demonstrated that TGT performed in samples of intoxicated rats complemented with normal plasma is a reliable tool for evaluation of VKA rodenticide PD in rats.

Topics: 4-Hydroxycoumarins; Animals; Anticoagulants; Blood Coagulation Factors; Blood Coagulation Tests; Female; Male; Rats; Rats, Sprague-Dawley; Rodenticides; Thrombin; Vitamin K

Vitamin K antagonists are used as rodenticides for pest control management. In rodents, prothrombin time is used to monitor their effect despite its limits and the emergence of many coagulation methods. The aim of this study is to explore different coagulation monitoring methods in order to propose the best method and the best parameter to monitor vitamin K antagonists effect in rodents. The coagulation function was thus monitored with global coagulation assays and specialty assays after difethialone administration in rats. Despite many parameters obtained by thromboelastometry, only clotting time and clot formation time obtained by ExTEM were modified. Their evolution was fast with doubling time respectively of 4.0h and 3.7h but their increases were delayed with a lag time higher than 8h. Conversely, prothrombin time evolution presented a lag time of only 2h, but a higher doubling time of 7.2h. The measurements of factor VII and X activities were the most sensitive assays to monitor vitamin K antagonists effect with almost no lag time and the fastest evolution. Nevertheless, factor X was shown to be the only key factor driving prothrombin time. Monitoring factor X activity enables to follow most effectively the anticoagulation status in rats after rodenticides administration.

Topics: 4-Hydroxycoumarins; Animal Feed; Animals; Anticoagulants; Blood Coagulation; Blood Coagulation Factors; Drug Resistance; Immunity, Innate; Liver; Male; Rats; Rats, Sprague-Dawley; Rodentia; Rodenticides; Vitamin K

Patients rarely consult physicians before developing coagulopathy or bleeding in most reported cases of superwarfarin intoxication. A 57-year-old woman ingested red-dyed pellets of anticoagulant rodenticide containing difethialone and warfarin as well as tablets of nitrazepam. Although she presented to the hospital in a comatose state, notable pink-colored excreta hinted at the consumption of anticoagulant rodenticide, which led to the early diagnosis of superwarfarin intoxication. Supplementation of large doses of intravenous and oral vitamin K successfully prevented coagulopathy and bleeding. On the other hand, temporary and reversible myocardial suppression was extremely severe, and required the introduction of percutaneous cardiopulmonary support.

Topics: 4-Hydroxycoumarins; Anticoagulants; Cardiomyopathies; Coloring Agents; Female; Humans; Intra-Aortic Balloon Pumping; Middle Aged; Nitrazepam; Rodenticides; Vitamin K; Warfarin