Rodenticide Poisoning
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Direct answer
Rodenticide poisoning in India frequently involves zinc phosphide, which releases toxic phosphine gas when it meets gastric acid, or anticoagulant rodenticides that deplete vitamin K dependent clotting factors. Zinc phosphide has no specific antidote, so care is supportive and centred on cardiovascular and respiratory monitoring. Anticoagulant rodenticides are treated with vitamin K1, with duration guided by the INR, because second generation agents remain in the body for weeks.
What you must remember
- Zinc phosphide: releases phosphine, which inhibits mitochondrial cytochrome oxidase; garlic-like breath, vomiting, shock, arrhythmias and pulmonary oedema follow.
- Acid avoidance: acidic fluids are avoided because they accelerate phosphine release from the stomach contents.
- Yellow phosphorus: causes hepatic necrosis, hypocalcaemia and hypoglycaemia, and the vomitus may glow in the dark.
- Vitamin K1: phytonadione is the antidote for anticoagulant rodenticides, given in high doses with duration set by the INR.
- Second generation agents: brodifacoum and bromadiolone have long half-lives, so prolonged vitamin K therapy and monitoring are needed.
- Blood products: fresh frozen plasma or prothrombin complex concentrate is reserved for major or life-threatening bleeding.
A worked emergency for a rodenticide ingestion with shock
A 28-year-old woman is brought after swallowing rodenticide powder, with garlic-smelling breath, repeated vomiting, a blood pressure of 80/50 mmHg and an irregular pulse.
- Secure the airway and circulation. Airway assessment and intravenous fluids come first, and acidic decontamination fluids are avoided.
- Send the right bloods. The electrocardiogram shows arrhythmia, so electrolytes, lactate and liver tests are sent, since zinc phosphide causes metabolic acidosis and hepatic injury.
- Give supportive care. There is no specific antidote, so care aims at perfusion, rhythm and pulmonary oedema.
- Identify the product. The clinician asks which product was used, because yellow phosphorus produces hepatic and calcium disturbances, and glowing vomitus is a clue.
Contrast a man with gum bleeding and a prolonged INR after eating bait. He needs a bleeding assessment and oral or intravenous vitamin K1, with dosing guided by the INR. If the INR fails to normalise after the vitamin is stopped, the agent matters, since second generation rodenticides need longer treatment.
Where the exam tries to catch you
Antidote choice and therapy duration are the two traps here.
- Trap: reaching for fresh frozen plasma first in anticoagulant bleeding. Correct: vitamin K1 is the mainstay because it restores synthesis of vitamin K dependent factors, whereas plasma gives only temporary replacement.
- Trap: choosing vitamin K3 as the antidote. Correct: examiners expect phytonadione, which is vitamin K1.
- Trap: equating zinc phosphide with aluminium phosphide. Correct: both release phosphine and share a garlic odour, but aluminium phosphide is more toxic and carries a higher mortality.
- Trap: assuming every anticoagulant poisoning settles in days. Correct: warfarin poisoning may settle within days, while second generation rodenticides need weeks of vitamin K1 guided by repeated INR testing.
Frequently asked questions
Why is acidic lavage avoided in zinc phosphide poisoning?
Zinc phosphide reacts with gastric acid to release phosphine gas, so acidic fluids can accelerate the release of this toxic gas. For this reason the stomach is not treated with acidic solutions, and management relies on supportive care with cardiovascular monitoring.
Which vitamin is the antidote for anticoagulant rodenticide poisoning?
Vitamin K1, given as phytonadione, is the antidote for anticoagulant rodenticide poisoning. Its duration is guided by the INR, because second generation agents such as brodifacoum and bromadiolone have long half-lives.
Which rodenticide causes hepatic necrosis and hypocalcaemia?
Yellow phosphorus causes hepatic necrosis, hypocalcaemia and hypoglycaemia, and its vomitus may glow in the dark. Treatment is supportive, with correction of electrolytes and close monitoring of liver function and clotting.
When are fresh frozen plasma or prothrombin complex concentrate used in rodenticide poisoning?
Fresh frozen plasma or prothrombin complex concentrate is reserved for major or life-threatening bleeding after an anticoagulant rodenticide. Vitamin K1 remains the mainstay, because it restores clotting factor synthesis over hours rather than providing temporary replacement.