Which of the following is a primary anticoagulant rodenticide?

• A. Warfarin
• B. Bromadiolone
• C. Zinc phosphate
• D. Cholecalciferol

Answer: (A)

The concept here is how a primary anticoagulant rodenticide works. These poisons kill by directly inhibiting the rodent’s blood clotting mechanism, causing fatal internal bleeding after ingestion. Warfarin is the classic example: it blocks the vitamin K cycle, so clotting factors II, VII, IX, and X can’t function. Without proper clotting, tiny injuries bleed out and the animal dies from hemorrhage. That direct action on the coagulation system makes it a primary anticoagulant rodenticide.

The other options do not kill by this anticoagulant mechanism. Zinc phosphate works mainly as a gastric irritant, causing death through digestive system injury. Cholecalciferol (vitamin D3) causes dangerous hypercalcemia, not impaired coagulation. Bromadiolone is also an anticoagulant, but it’s typically discussed as a second-generation anticoagulant; the classic primary example remains warfarin for this specific distinction.