Clinical challenges of management of a coumarin rodenticide (brodifacoum) toxicity vs. warfarin toxicity: case report

Excerpt

Objective To report the clinical course of a man who reportedly ingested nine ounces of a coumarin rodenticide (brodifacoum) and the clinical challenges of management, specifically the differences from the management of typical warfarin overdose. Case summary A 60 year old man who presented to the hospital with a one-week history of hematuria, and lower back pain with screening labs documented an INR >5.5 and resulting in admission found to have ingested nine ounces of brodifacoum containing rodenticide. Over this 14-day course of admission, he was treated with 18 units of fresh frozen plasma and seven units of packed red blood cells. Phytonadione doses were progressively increased due to inadequate response. Stabilization (INR 1.4) was finally achieved with 50 mg three times daily, which was used as the discharge dose. Discussion There are numerous case reports of brodifacoum toxicity in humans, and although brodifacoum is an anti-coagulant, the management of brodicafoum toxicity is quite different from the management of warfarin toxicity. Brodifacoum belongs to a class of drugs called “super-warfarins” and has an elimination half-life of approximately 40–130 days due to its increased lipophilicity (not unlike amiodarone) and more effective blockade of the vitamin K-1 epoxide cycle than warfarin. As with all coumarins, phytonadione is the treatment for brodifacoum toxicity. The specific dosage of phytonadione that will be required to treat the toxicity will vary based on the patient and the amount of brodifacoum ingested, and must be titrated on an individual basis based on serial INR testing. Phytonadione therapy must be continued for several months in order to prevent relapse as the brodifacoum is released from fat stores. Based on various case reports, doses as high as 800 mg per day may be required for an extended period. Conclusions The management of brodifacoum toxicity requires patient-specific dosing of phytonadione, with titration based on serial INR testing. Unlike warfarin toxicity which is typically treated with single doses of 2–10 mg of phytonadione, therapy with phytonadione is required in much higher doses up to 800 mg per day for brodifacoum toxicity. Therapy must also be continued for a much longer period of time due to the long elimination half-life of brodifacoum. …